Nuclear Physics News Volume 18/No

Nuclear Physics News Volume 18/No. 4

Nuclear Physics News is published on behalf of the Nuclear Physics European Collaboration Committee (NuPECC), an Expert Committee of the European Science Foundation, with colleagues from Europe, America, and Asia.

Editor: Gabriele-Elisabeth Körner Editorial Board T. Bressani, Torino S. Nagamiya, Tsukuba R. F. Casten, Yale A. Shotter, Vancouver P.-H. Heenen, Brussels (Chairman) H. Ströher, Jülich J. Kvasil, Prague T. J. Symons, Berkeley M. Lewitowicz, Caen C. Trautmann, Darmstadt Editorial Office: Physikdepartment, E12, Technische Universitat München, 85748 Garching, Germany, Tel: +49 89 2891 2293, +49 172 89 15011, Fax: +49 89 2891 2298, E-mail: [email protected]

Correspondents Argentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Austria: H. Leeb, Vienna; Belgium: G. Neyens, Leuven; Brasil: M. Hussein, São Paulo; Bulgaria: D. Balabanski, Sofia; Canada: J.-M. Poutissou, TRIUMF; K, Sharma, Manitoba; C. Svensson, Guelph: China: W. Zhan, Lanzhou; Croatia: R. Caplar, Zagreb; Czech Republic: J. Kvasil, Prague; Slovak Republic: P. Povinec, Bratislava; Denmark: K. Riisager, Århus; Finland: M. Leino, Jyväskylä; France: G. De France, GANIL Caen; M. MacCormick, IPN Orsay; Germany: K. Langanke, GSI Darmstadt; U. Wiedner, Bochum; Greece: E. Mavromatis, Athens; Hungary: B. M. Nyakó, Debrecen; India: D. K. Avasthi, New Delhi; Israel: N. Auerbach, Tel Aviv; Italy: M. Ripani, Genova; L. Corradi, Legnaro; Japan: T. Motobayashi, RIKEN; Mexico: J. Hirsch, Mexico DF; Netherlands: G. Onderwater, KVI Groningen; T. Peitzmann, Utrecht; Norway: J. Vaagen, Bergen; Poland: B. Fornal, Cracow; Portugal: M. Fernanda Silva, Sacavém; Romania: V. Zamfir, Bucharest; Russia: Yu. Novikov, St. Petersburg; Serbia: S. Jokic, Belgrade; South Africa: S. Mullins, Cape Town; Spain: B. Rubio, Valencia; Sweden: J. Nyberg, Uppsala; Switzerland: K. Kirch, PSI Villigen; United Kingdom: P. Regan, Surrey; USA: D. Geesaman, Argonne; D. W. Higinbotham, Jefferson Lab; M. Thoenessen, Michigan State Univ.; H. G. Ritter, Lawrence Berkeley Laboratory; G. Miller, Seattle.

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Vol. 18, No. 4, 2008, Nuclear Physics News 1 Nuclear Physics Volume 18/No. 4 News

Contents Editorial ...... 3 Laboratory Portrait The Nuclear Physics Laboratory at CEA DAM Ile-de-France by Eric Bauge ...... 5 Feature Article Deep Underground Laboratories—Somewhere Quiet in the Universe by Neil Spooner ...... 13 Facilities and Methods JUSTIPEN—The Japan U.S. Theory Institute for Physics with Exotic Nuclei by David J. Dean ...... 21 Compass and the Nucleon Spin Puzzle by Bradamante...... 26 Impact and Applications Industrial PET at Birmingham by David Parker ...... 33 Meeting Reports The 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics—CGS13 by Kris Heyde ...... 37 Hadron Physics Summer School 2008 by Frank Goldenbaum...... 38 News and Views ...... 40 Calendar...... 44

Cover illustration:

2 Nuclear Physics News, Vol. 18, No. 4, 2008 editorial

OECD Global Science Forum Report on Nuclear Physics

Globally about $2B is spent annu- was chaired by Dennis Kovar. Its rec- strongly endorses this international- ally for Nuclear Physics research. ommendations set the backdrop ization of our science and recom- Over 13,000 scientists, engineers, against which the funding agencies mends that “free and open access to and students involved in research car- will plan investment in our field for beam usage should continue to be the ried out primarily at the 90 major the next decade. international mode of operation for accelerator facilities with user pro- The report draws attention to the nuclear physics facilities.” The report grams, but also at a range of smaller, major advances that have occurred in also notes that our community has specialized facilities that provide for the decade since the last report was effectively developed a worldwide national needs. This is a truly enor- published, highlighting of particular roadmap for the development of the mous human endeavor and it is interest: the observation of a new subject. Particularly important in this sobering to think that our science jus- state of matter in the form of the regard are the periodic Long Range tifies such a commitment of QGP, the confirmation from solar Plans prepared in Europe by NuPECC resources. neutrino measurements that neutrinos (www.nupecc.org/pubs/lrp03/long_ This rather startling insight is one have mass, and the explosion of range_plan_2004.pdf) and in the of a number of interesting results knowledge regarding exotic nuclear United States by NSAC (www.sc.doe. from the efforts of the Working structure and nuclear astrophysics gov/np/nsac/nsac.html). The report Group on Nuclear Physics, estab- made possible by the advent of radio- finds that “this global roadmap lished by the Global Science Forum active beam facilities. The working reflects a high degree of coordination of the OECD (Organisation for Eco- group assessment for the next decade in optimizing the available resources nomic Co-operation and Develop- is equally bright, with the main chal- for the world-wide nuclear physics ment). Their report was published lenges summarized in a series of programme.” The working group earlier this year and can be accessed questions: Is QCD the complete the- suggests that a mechanism should be at www.oecd.org/sti/gsf. ory of the strong interaction? What established to review this global The Global Science Forum pro- are the phases of nuclear matter? roadmap on a regular basis and provides a venue for communication What is the structure of nuclear mat- poses that WG9, the IUPAP Working between senior science policy offi- ter? What is the role of nuclei in Group on Nuclear Physics, might cials and the Forum’s activities pro- shaping the evolution of the uni- take on this role. duce findings and recommendations verse? What physics is there beyond As noted earlier, these periodic for action by governments, interna- the standard model? OECD reports do exert influence tional organizations, and the scien- The section of the report that will over the direction in which our field tific community. The last report on perhaps be of most interest to our develops, because they are reports Nuclear Physics was by the Working funding agencies (and so impact commissioned by, and accepted by, Group on Nuclear Physics (1996– directly on our ambitions as scientists) our funding agencies. For this reason 1999) chaired by Bernard Frois and relates to international cooperation they form valuable reading for the highlighted the enormous potential and strategic planning. The working research community. Indeed, the that the development of radioactive group observes that international present report has already had beam facilities would provide for cooperation has long been the norm in noticeable effects. Colleagues in nuclear physics research. That report our science and as evidence for this Asia have recognized the benefits of provided the background for the last notes the large external user presence regional planning and are in the round of large-scale investment in at major national facilities (for exam- process of establishing a version of our field. The present Working ple GSI 40%, RHIC 50%, CEBAF NuPECC that will allow Asian Group was established in 2006 and 40%, and TRIUMF 66%). The report countries to extend cooperation and

The views expressed here do not represent the views and policies of NuPECC except where explicitly identified.

Vol. 18, No. 4, 2008, Nuclear Physics News 3 editorial

develop regional plans, and WG9 has already discussed the proposal that they take on the role of preparing and updating a global roadmap for the field based on the regional planning. Such moves are timely, for while our field is currently at a stage where the scale of facilities can be accommodated on a regional basis, some of the ambitious plans that are emerging (e.g., for Electron Ion Colliders or next generation ISOL facilities) may need to be considered on a world basis.

BRIAN FULTON DENNIS KOVAR NuPECC Chair DOE Former Associate Director of Science for Nuclear Physics

4 Nuclear Physics News, Vol. 18, No. 4, 2008 laboratory portrait

The Nuclear Physics Laboratory at CEA DAM Ile-de-France

Introduction • Studies on short-lived nuclear states 4MeV. Possible Xe+ ions beam was The Nuclear Physics Laboratory or isomers, including their interac- added in the eighties on a specific (Service de Physique Nucléaire, SPN) tions with laser-induced plasmas. beam-line. Pulsed or continuous ion belongs to the Military Application • Nuclear data for applications and beams are available. In pulsed mode, Division (Direction des Applications their covariances. the repetition rate is fixed at 2.5 MHz militaries, DAM) of the French (400 ns) and the FWHM is about 10ns. Atomic Energy Commission (Com- Naturally, these four topics exhibit some Attached to that accelerator are five missariat à l’Energie Atomique, overlap. For example, fission studies beam-lines serving the two experimen- CEA). It is located in the DIF (DAM have a strong impact on nuclear data tal rooms. One of these beam-lines is Ile de France) research center in works, or the many-body calculations of dedicated to the neutron production Bruyères-le-Châtel, 30km south of Paris. nuclear structure produce results that are with a Mobley buncher (to reduce the The laboratory houses 44 staff further used in fission, isomer, or FWHM of the pulsed beam to 1–2 ns), members, plus several PhD students, nuclear data studies. Actually, that over- a capacitive beam pick-off detector (to post docs, and foreign visitors. Its pro- lap between topics is a clear manifesta- measure that FWHM) and two NE213 grams range from support to the DAM tion of the complementarities and strong and BF3 detectors, to monitor the neu- Simulation program, to fundamental interactions between the SPN physicists. tron flux on-line. Mono-energetic neu- experimental and theoretical nuclear Nevertheless, those internal com- trons are created by nuclear reactions physics studies. The originality of plementarities do not preclude collab- between the accelerated 1H+, 2H+ ions, SPN actually resides in that continu- orations, as evidenced by our strong with thin layer of lithium, or deute- ous coverage of the whole spectrum of involvement in many national and rium, or tritium-loaded Ti. Neutron nuclear physics from fundamental international collaborative efforts. energy is defined by the specific reac- studies to applied physics. Before going into each of the four tions and by choosing the appropriate Since its creation, almost 50 years main topics, the present article shall angle. The range of energy is 30 keV ago, most of the scientific activities, first detail our on-site experimental to 20 MeV and the neutron emission especially the experimental ones, facilities as well as our current array rate is of the order of 107 n/s/sr. involve the neutron; either as an incom- of detection systems. That accelerator is shared in the ing or an outgoing particle, and many EFNUDAT [1], 6th Framework Euro- (n,γ), (n,n’), (n,xn), or (n,f) cross-sec- Facilities pean program for encouraging transna- tions have been measured in Bruyères- Besides the aforementioned four tional access to nuclear physics le-Châtel. Theoretical studies were also main research topics, SPN also oper- infrastructure among member countries. initiated long ago in the domains of ates a KN4000 4 MV Van de Graaff SPN is also strongly involved in the nucleon–nucleus reactions and micro- electrostatic accelerator facility for project of the future NFS (Neutron For scopic nuclear structure theory. applications like measurement of neu- Science) neutron source that should be Today, the programs carried out in tron cross-sections, neutron or gamma constructed as a part of the SPIRAL2 SPN can be roughly grouped into four detector calibrations, and chemical facility in GANIL (Caen, France) in the main research directions: analysis of matter using ion beams. year 2012. That NFS neutron source That facility is used in support of will deliver neutrons in a continuous • Theoretical studies of the nuclear many of the experimental studies pur- spectrum peaking near 20 MeV with many-body problem with applica- sued at SPN. intensities much stronger than that of tions to both nuclear structure and The 4 MV Van de Graaff is an the other European facilities (Gelina, nuclear reactions. HVEE-electrostatic accelerator that nTOF) in that energy range. • Experimental and theoretical stud- delivers 1H+, 2H+, 3He+, and 4He+ ions Finally, for theoretical studies, ies of the fission phenomenon. within the energy range 420 keV to computing facilities constitute the

Vol. 18, No. 4, 2008, Nuclear Physics News 5 laboratory portrait

of polyethylene and 4mm of inner boron carbide). Its detection efficiency is 50% from fission neutron from 252Cf. Although this detector is mainly a counter, it is able to provide a rough estimate of neutron spectra. Such an instru- Q1 ment can be used for fission studies and (n,xn) reaction measurements. The Lead Slowing Down Spectrom- eter (LSDS) installed on the WNR neutron source at the Los Alamos National Laboratory (USA) was first operated in Bruyères-le-Châtel as the CIRENE assembly. At that time, it was devoted to isomeric ratio measurements in the resonance region. Its installation at the WNR intense source gives the opportunity to measure cross-sections on very small Figure 1. The 4 MV Van de Graaff electrostatic accelerator of SPN (open with matter quantities (down to 10ng), or to the visible glowing ion source). measure very small cross-sections for neutron energies ranging from 0.1eV to counterpart to experimental facilities. mainly by the Gd nuclei. In the case of 100keV. That method was first demon- CEA DAM Ile-de-France hosts two CARMEN, the neutron detection is strated in 1955 [3]. It profits from the high-performance computing centers, spread over the 50μs following the great probability for neutrons to scatter CCRT and TERA, which allow us to nuclear reaction (99% of the neutrons elastically in natural lead, and from the develop ambitious theoretical programs are captured at that time). This time very strong time/energy correlation that require large amounts of computing spreading allows for counting neutrons within the cube. The gradual slowing of power. even for high-multiplicity events. Hence neutrons in the cube produces a gain in this detector is adequate for (n,xn) mea- apparent neutron flux of the order of 103 Detection Systems surements. CARMEN is a high- compared to usual time of flight bases. SPN currently operates three major efficiency detector (85% efficiency for In this way the useful neutron flux on detector systems. 252Cf fission neutrons). Moreover, the the LSDS at Los Alamos can be as high The CARMEN detector (Cells distance between the two hemispheres as 4.1010 n/cm2/s. Arrangement Relative to the Measure- can be adjusted according to the experiment of Neutrons) [2] is a large organic ment’s needs. This peculiarity allows Theoretical Nuclear scintillator tank-type detector devoted to measurements of neutron spectra corre- Many-Body Problem neutron counting. It is the continuation lated to neutron multiplicity. The theoretical treatment of of a long SPN tradition since the first Since the beginning of 2008, we nuclear structure with mean-field- neutron counting ball was built in 1964 have been developing a 3He based neu- based approaches has long been a by M. Soleilhac. CARMEN consists of tron counter. It consists of a specificity of our laboratory. The her- two independent vertical hemispheres, 50*50*75cm3 polyethylene block with itage of pioneering works of Daniel each one equipped with 12 photomulti- 23 inserted 10 bars 3He proportional Gogny on the effective nuclear inter- pliers. The active part which is a gado- counters. This device works similarly to action [4] and its use within the linium-loaded scintillating organic CARMEN: neutrons are first moderated frameworks of mean-field [5] and liquid (BC521) has a total volume of in polyethylene before reacting with the beyond-the-mean-field theories is still 1m3. Like in many detectors of this 3He counters. It is nevertheless com- living. Those theories constitute a type, neutrons are moderated in the pletely insensible to gamma rays. It also base on which are built modern funda- organic liquid before being captured possesses an external shielding (10cm mental developments. These theories

6 Nuclear Physics News, Vol. 18, No. 4, 2008 laboratory portrait

exhibit a strong predictive power that use of approaches based on HFB and approach is triple: experiments, theory can be challenged by experimental data collective dynamics for fission studies. and nuclear data evaluation. like mass or nuclear spectroscopy of Another example resides in the growing stable and unstable nuclei. The current use of ingredients derived from theoret- Experimental Fission Studies thrust in those studies consists in using ical nuclear structure studies in reaction A program for measuring fission the Gogny interaction in approaches models, such as level densities derived neutron energy spectrum and multiplic- that include more and more correla- from single particle levels or nuclear ity in neutron-induced fission in the tions beyond the single-particle picture matter radial densities in finite nuclei. 1–200 MeV range has been initiated at of the mean field approximation. Such These will be discussed in the section the Los Alamos Neutron Science Center approaches are for example Quasi- on “nuclear reaction modeling.” (LANSCE). This work provides unprec- Particle Random Phase Approximation edented data for 238U, 235U, and 237Np (QRPA) [6], multi-particle multi-hole Fission [14], the interpretation of which is per- configuration mixing [7], or Generator SPN has been involved in the study formed in conjunction with the theorists. Coordinate Method (GCM) [8]. The of fission for many years. The works More complex experiments including nuclear properties predicted within these by Fréhaut and collaborators about fission fragment mass measurements are theoretical frameworks are then com- 30 years ago on fission neutron multi- foreseen. Fission is also studied on the pared with the latest experimental data plicity measurements from the reso- spallation-driven LSDS. on unstable nuclei, allowing us to con- nance region up to 28MeV are still a The group is also at the origin of a tribute to the fundamental understanding basic reference [12]. In the field of the- novel experimental project to be per- of nuclear stability, the persistence or ory, the pioneering work of Berger etal. formed at the ELISE Electron–ion erosion of (sub-)shell gaps far from the was the first to achieve a microscopic collider to be constructed at FAIR the beta stability line, giant resonances, and description of the scission of fissioning future facility at GSI, Darmstadt. The nuclear shape coexistence [9]. systems, as well as the transition from goal of this reverse kinematics experi- Another theme of study consists in fission to the fusion valley [13]. ment is to measure event by event the large-scale systematic calculations of Today, nuclear fission is one of the main fission observables with an nuclear properties, which provide a main research fields in SPN. The unprecedented precision: unambiguous wealth of results that can be exploited to get a better picture of the global evolution of nuclear properties across the chart of nuclei [10]. These studies are made possible by the availability of massive amounts of computing power at the CCRT and TERA computing centers. Our website (http://www- phynu.cea.fr) presents extensive calculations of the stable and unstable nuclei Q1 as they are predicted, from drip-line to drip-line, within axially symmetric Har- tree-Fock-Bogoliubov (HFB) framework using the Gogny D1S interaction. The D1S interaction itself is pres- ently under review, and several improvements to that interaction are currently investigated [11]. Another trend in the nuclear many- body problem is the convergence of structure and reaction studies. A first Figure 2. The Lead Slowing Down Spectrometer installed at the WNR neutron example of such a convergence is the source in Los Alamos National Laboratory.

Vol. 18, No. 4, 2008, Nuclear Physics News 7 laboratory portrait

separation in mass and charge of both 2015 in GANIL, or at the projected ments properties at each point of that fragments, fragment kinetic energy, fis- EURISOL facility. That availability of scission line [16]. That potential energy sion neutron multiplicity, and energies fission fragment beams will eventually surface can also be further used as a for tens of actinides and subactinides. produce strong experimental constraints potential for the dynamical solving [17] The detectors required for the project for theoretical nuclear structure, as well of the time-dependent Schrödinger equa- are currently being designed. This as key ingredients for fission studies tion for the collective wave function of experiment is expected to be a real relative to the prompt and delayed the fissioning nucleus. By calculating the breakthrough in the experimental study decay of fission fragments. flux of that wave function transmitted of nuclear fission and to enrich very sig- through the scission line, fission frag- nificantly both quantitatively and quali- Theoretical Fission Studies ment yields can be predicted using only tatively our knowledge on the fission The theoretical counterpart to the the Gogny effective interaction as input. mechanism and at the same time the fission measurements described earlier The theoretical fission fragment yields data bases required for applications. consists in attempting to understand calculated in this manner are qualita- In a more applied field, a program in and describe the observables associated tively close to experimental values. collaboration with the CEA/IRFU in with the fission process using micro- Finally, the prompt neutron and Saclay for characterizing the delayed scopic theoretical physics approaches. gamma emission can be predicted by neutron emission in gamma-induced fis- Approaches built on the established allowing the fission fragments (of sion is carried on for a selection of many-body treatment of nuclear struc- which the yields and characteristics are actinides. The purpose is to provide data ture (see the earlier section “Theoretical calculated above) to decay according to for libraries and evaluations in the frame- Nuclear Many-Body Problem”) are the statistical model. Again, the observ- work of applications for nuclear material developed today. In the mean-field ables calculated in this way are qualita- detection in freight transportation [15]. framework, the potential energy of the tively comparable to experimental data. In the future, the structure of fis- fissioning nucleus can be calculated as a That qualitative agreement shows that sion fragments will be extensively function of collective coordinates (like the leading order effects are all studied at projected facilities such as elongation, asymmetry, etc.). This poten- included properly in the calculations. SPIRAL2, which is scheduled to tial energy surface can then be used to Besides the obvious thematic over- produce its first radioactive beam in specify a scission line and fission frag- lap with nuclear data for applications, fission is also a formidable laboratory to challenge our understanding of fundamental nuclear structure. For example, fission modeling involves large amplitude collective motion of the nucleus, dynamic coupling between several collective modes, as well as between collective and individual (particle-hole) degrees of freedom. The theoretical and experimental studies of fission are thus strongly linked to the Q1 more fundamental understanding of the static and dynamic structure of nuclei far from equilibrium configurations.

Nuclear Physics in Plasmas, Nuclear Physics with Lasers, and Nuclear Isomers Figure 3. Mean energy of prompt fission neutron for the 238U(n,f) reaction The isomeric states play an impor- measured at LANSCE (symbols) as a function of the incident neutron energy tant role in nuclear physics. Nuclear compared with model calculations (curve). isomers are very good probes to study

8 Nuclear Physics News, Vol. 18, No. 4, 2008 laboratory portrait

nuclear structure, because of their usu- to prepare reverse kinematics experi- leading to the de-excitation of the iso- ally pure or quasi-pure single particle ments at the future SPIRAL2 radioac- mer. This process is called neutron configurations. The experimental infor- tive beam facility. These experiments super-elastic scattering. mation collected in those studies is of rely on the Time Dependent Perturbed To address this process study, col- course compared to the predictions of Angular Distribution (TDPAD) laboration between CEA laboratories nuclear structure theoretical models, method in combination with heavy produced a 177 mLu target at the Institut and contributes to their experimental ion-γ correlations. This method takes Laüe Langevin in Grenoble by ther- validation. advantage of the perturbation of the mal neutron irradiation of a highly Moreover, the understanding of aligned spin of the isomeric state enriched (99.993%) 176Lu powder. the formation and de-excitation of induced using external magnetic or Following the irradiation period, the nuclear isomers is a scientific chal- electric fields. sample was cooled down to remove lenge. Our laboratory is involved in Several magnetic and quadrupole the 177Lu ground state, which is short various fields, centered on the iso- electric moments have been measured lived (6.647 ± 0.004 days) compared mers’ properties: nuclear moment in the region of neutron rich nuclei to the isomeric state (160.44 ± 0.06 measurement, interaction processes mainly located around the N = 28 and days). Finally, nanograms of Lute- between isomer and neutron, and iso- N = 4 0 (sub)-shell closures. tium, 1014 atoms, were extracted by mer excitation in plasmas. chemical separation before producing Neutron–Isomer Interaction the isomeric targets by a direct deposit Nuclear Moments of Isomeric Nuclei Nuclear isomers are promising method on backings. Measurement of electromagnetic candidates to store and release energy To measure the super-elastic cross- moments is of wide interest in sub- on request. However, the induced de- section at neutron thermal energy, we atomic physics. In nuclear physics, excitation of isomers comes up against used an original method involving two within the extremely simplified single- an antagonism: the higher the isomer types of measurements: the isomer particle model, magnetic moments of half life the more difficult de-excitation radiative capture cross-section and the odd mass nuclei are directly linked to is. The induced de-excitation of K iso- isomer burn-up cross section. The the orbital occupied by the unpaired mers may be different because the super-elastic cross-section, 258 ± 58 b, nucleon. Measuring such moments half-life of K-isomers is not only due was obtained by subtracting the radia- thus allows one to unambiguously to the spin difference but also to the K tive capture cross-section from the probe nuclear structure and its evolu- difference (K is the projection of the burn-up cross-section. This is the tion throughout the nuclear chart. The total nuclear spin on the symmetry highest value ever measured for this electric quadrupole moment is more axis in deformed nuclei). At low exci- process. The ratio between the super- sensitive to the collective nature of the tation energy, K can be approximated elastic and radiative cross-sections is state, and is a good observable to to be a good quantum number and the close to 0.6, showing the importance quantify nuclear deformation. nuclear transitions depend on K of the neutron-induced de-excitation Our laboratory is specialized in conservation. At neutron separation channel. This encouraged us to pursue measuring both magnetic and electric energy, a complete disappearance of K investigations by directly measuring quadrupole moments of isomeric quantum number is expected. Hindered the super-elastic process. That pro- states, and is part of the “g-rising” col- transition between two states with a gram is in progress at the Orphée reac- laboration. To perform such experi- large K difference could thus be cir- tor in Saclay. ments, one should first produce nuclei cumvented via the formation of a in isomeric states of interest with suf- compound nucleus. Nuclear Excitation in Plasma ficient spin alignment. To do so, sev- The 160-day 23/2− isomer in 177Lu The last decade witnessed a fast eral kinds of nuclear reaction are at located at 970 keV is a candidate for development of power lasers that now our disposal: fragmentation reactions observing an induced de-excitation by allow studying matter in extreme den- (GANIL, GSI, MSU), fission frag- neutron scattering. During a collision sity and temperature conditions. With ments (GSI, ILL), and (d,p) particle between a neutron and an isomer, the these lasers, it has become possible to transfer reactions in direct kinematics nucleus can partly transfer its excita- create plasmas at high enough tem- (Orsay, Bruyères-le-Châtel) in order tion energy to the scattered neutron peratures to induce high fluxes of

Vol. 18, No. 4, 2008, Nuclear Physics News 9 laboratory portrait

de-excitation may occur with significantly different lifetimes.

Nuclear Data The fundamental knowledge of Q1 nuclear physics is not directly usable for applications such as energy production using thermal or fast spectrum fission reactor (GEN IV project), fusion studies (ITER), shielding, medical, geological, and space applications. For that purpose, the available experimental and theoretical information must be synthesized into the so-called evaluated nuclear data files. Across the world, several approaches of that synthesis Figure 4. Potential energy surface of the 238U fissioning nucleus calculated as a process (called evaluation) are put into function of the quadrupole and octupole collective coordinates, within the HFB practice. SPN has chosen to focus on framework using the D1S effective interaction. an approach that uses the results of nuclear reaction models, whose parameters are constrained by experimental energetic particles in a highly ionized their transition energies are closely data. This approach implies dedicated medium. matched. This can accelerate the de- work on nuclear reaction models on the Under these conditions, the atomic excitation of the excited nuclear level, one hand, and nuclear reaction experi- nucleus is not left unperturbed. On the and reduced its lifetime. mental data on the other hand. one hand, the plasma particles can We developed a model able to deal induce nuclear reactions, and on the with these processes in plasma under other hand, the modification in the thermodynamic equilibrium. It evalu- Nuclear Reaction Modeling electronic environment of the atom ates internal conversion, NEEC, and Because nuclear reaction models greatly modifies interaction processes NEET rates in plasma. Depending on are at the heart of our nuclear data eval- between the nucleus and the atom, such the particular situation, we used an uation process, they constitute an as nuclear lifetime and reaction rates. average atom description or a Multi important focus of our laboratory. In the For heavy nuclei, the nuclear life- Configuration Dirack Fock (MCDF) continuum region (above the resonance time of discrete levels is often strongly approach to describe the electronic region), the relevant nuclear models dependent on internal conversion, environment of the atom. Large varia- are the optical model for direct reac- which involves bound electrons. In tions of several excited nuclear-level tions, pre-equilibrium models, and the plasma, many of these electrons are no lifetimes have been predicted. For statistical Hauser-Feshbach decay of longer in a bound state and the internal example, the first excited state of the compound nucleus. conversion rate can be significantly 201Hg, an excited level lying Depending on the availability of reduced. Its coupling with its inverse 1.565 keV above ground state, has a enough experimental data to constrain process (Bound Internal Conversion), de-excitation lifetime that increases the model parameters, two options are Nuclear Excitation by Electronic Cap- from 81 ns under laboratory condi- open for the modeling of nucleon- ture (NEEC), can lead to greatly tions up to 1 ms when the plasma tem- induced direct reactions. When exper- increased nuclear lifetimes. peratures reaches around 1 keV imental constraints are available, the In some cases, an atomic transition (Figure 5). A complete description of dispersive phenomenological optical can be coupled with a nuclear transition the nuclear lifetime must also include model potential [18] allows very pre- in a process called Nuclear Excitation some other nuclear levels through cise restitution of experimental scat- by Electronic Transition (NEET) if which indirect nuclear excitation or tering measurements. Conversely, if

10 Nuclear Physics News, Vol. 18, No. 4, 2008 laboratory portrait

experimental data is unavailable, aerospace applications. Such calcula- detector was specially designed for direct reactions observables can be tions can be performed using the such studies and was used in coinci- predicted with the semi-microscopic BRIC-BRIEFF [24] intra-nuclear cas- dence with NE213 neutron detectors. optical model potential [19], built cade code. That code has recently been These measurements were performed using nuclear radial densities obtained extended toward incident nucleon ener- between 8.3 and 13.3 MeV on Bi and from HFB theoretical nuclear struc- gies as low as 14 MeV, which overlap Ta targets [2]. ture calculations. In between these with the energy region where the The neutron–deuteron interaction two lies the global phenomenological TALYS code is relevant, allowing for is also under experimental investiga- optical model potential [20], which is inter-comparisons between codes. tion in parallel to theoretical studies. widely used due to its ease of use as A rigorous calculation of the neutron- well as its globally good quality. For induced deuteron break-up cross-section deuteron-induced direct reactions, the Experimental Nuclear Data was carried out for neutron energies CDCC (Continuum Discretized Cou- Measurements up to 30 MeV. The quality and consis- pled Channels) approach [21] has Experimental nuclear data is tency of the existing experimental and been developed to explicitly take into essential to constrain as well as vali- evaluated data lead us to believe that account the break-up of the weakly date the nuclear reaction models the evaluated cross-section of the bound deuteron. described earlier. Besides the fission neutron-induced deuteron break-up An essential ingredient of the experimental works, which are already exhibits uncertainties of the order of modeling of the statistical compound covered in the section on experimental 20–30%. New and more accurate nucleus decay is the level density of fission studies, the (n,xn) reaction is the experimental data are thus necessary to each possible final state of the com- prominent non-elastic process for fast cover the 5–10 MeV and 15–30 MeV pound nucleus. To go beyond the neutrons incident on non-fissionable energy ranges. adjusted level density formulae based nuclei. For example, in the 7–20 MeV Such measurements were per- on the Fermi gas model, a combinato- energy range the (n,2n) reaction is one formed on the low background and rial approach [22] that uses single-par- of the most important nuclear-reaction collimated beam-line of the Tandem ticle levels from HFB structure channels. Simulation codes involve 7 MV accelerator (now decommis- calculations has been developed. several models (optical model, direct sioned) in Bruyères-le-Châtel. A scin-

The aforementioned ingredients interaction, pre-equilibrium, and evapo- tillation detector C6D6 is used as are combined in the TALYS [23] ration) to reproduce the whole reaction deuteron target and is set up within the nuclear reaction code, which is devel- process. Among these processes, the reaction chamber of the CARMEN oped in collaboration with NRG Petten pre-equilibrium is clearly the least detector that allows one to count the (Netherlands). TALYS includes many well known. Although some of the number of outgoing neutrons emitted state-of-the-art nuclear reaction models existing models are able to reproduce to cover all the main reaction mecha- integrated observables, differential nisms encountered in light particle- measurements are more challenging. induced reactions up to 200 A MeV. It In order to provide experimental can provide a complete description of information relevant to the pre- all the open reaction channels with only equilibrium process, we have per- a minimal input (4 lines), but can also formed an original measurement of be operated in expert mode using many the energy spectra of neutrons in (over 250) keywords that specify (n,xn) reactions in coincidence with options and parameters for the nuclear neutron multiplicity. Contrary to model calculations. “classical” (n,xn) reaction measure- The modeling of high-energy reac- ments where all the channels emit- tions is also of interest for applications ting at least one neutron are taken like Accelerator Driven Systems, into account, the double differential shielding, or assessment of effect of cross-section in (n,2n) tagged reac- Figure 5. Nuclear lifetime of the high-energy particle on electronics in tions are extracted. The CARMEN isomeric level of 201Hg.

Vol. 18, No. 4, 2008, Nuclear Physics News 11 laboratory portrait

in a D(n,2n) reaction. A NE213 detec- Decay Data and Fission Yields Peaceful Uses of Atomic Energy, tor is placed in the beam to monitor sub-library. Geneva, vol 4, 1995, p 135. the neutron flux, and ensures the nor- The next frontier in the field of 4. J.F. Berger, M. Girod, D. Gogny, malization of the measured D(n,2n) evaluated data consists not only in Comput. Phys. Comm. 63, 365 (1991). 5. J. Dechargé, D. Gogny, Phys. Rev. C cross-section. providing the best possible nuclear 21, 1568 (1980). data based on the synthesis of the 6. S. Peru, H. Goutte, Phys. Rev. C 77, available experimental and theoreti- 044313 (2008). Evaluation Activities cal knowledge, but also in estimating 7. N. Pillet, J.F. Berger, E. Caurier, Phys. The last step in the evaluation pro- the uncertainties associated with Rev. C 78, 024305 (2008). cess consists in using nuclear reac- these evaluated data. These uncer- 8. E. Clement et al., Phys. Rev. C 75, tions codes to produce evaluated data tainties are used to assess the operat- 054313 (2007). 9. J.P. Delaroche et al, Nucl. Phys. A 771, files that are consistent with the avail- ing margins of future nuclear energy 103 (2006). able experimental information, thus projects like the GEN IV nuclear 10. G.F. Bertsch et al. Phys. Rev. Lett. 99, synthesizing the theoretical and exper- reactors. The rigorous estimation 032502 (2007). imental knowledge of the day. For [26] of these uncertainties needs to 11. F. Chappert, M. Girod, S. Hilaire, present day nuclear energy applica- take into account both the dispersion Phys. Lett. B 668 420 (2008). tions, the most important reactions are and error bars of experimental data, 12. Fréhaut et al., EXFOR reference W, of course the neutron-induced reac- as well as the uncertainties associated Frehaut, 8009. 235,238 13. J.F. Berger et al., Nucl. Phys. A428 tions on the major actinides U with the models and their parameters. and 239Pu. These involve adjusting 23c (1984). A large international effort is under- 14. T. Ethvignot et al., Phys. Lett. the many parameters associated with way to produce uncertainty informa- B575,221 (2003); T. Ethvignot et al., the phenomenological modeling of the tion for the new files in the future PRL 94, 052701 (2005); J. Taieb et al., fission process [25] using constraints JEFF 3.2 release. Proceedings of the Nuclear Data Con- coming from both nuclear physics ference, Nice 2007. 15. D. Doré et al., Proceedings of the experiments and critical assembly Conclusions Nuclear Data Conference, Nice 2007. integral experiments. We collaborate The Service de Physique Nucléaire with CEA DEN Cadarache on both the 16. N. Dubray, H; Goutte, J.P. Delaroche, of the CEA DAM Ile-de-France Phys. Rev. C 77, 014310 (2008). validation of nuclear data files and contributes equally to the advance- 17. H. Goutte et al., Phys. Rev. C 71, their extension toward the resonance ment of knowledge in fundamental 024316 (2008). region. Once a nuclear data file is and applied nuclear physics. SPN is 18. B. Morillon, P. Romain, Phys. Rev. C complete and validated it is submitted deeply involved in many collabora- 70, 014601 (2004). to the JEFF (Join European Fusion tions, both present and future, within 19. E. Bauge, J. P. Delaroche, M. Girod, Phys Rev. C 63, 024607 (2001). Fission) project, to be further tested CEA, in France, in Europe, and and eventually included in the JEFF 20. A.J. Koning, J. P. Delaroche, Nucl. internationally. The theoretical and Phys. A 713, 231 (2003). nuclear data library (NDL). The JEFF experimental studies performed in 21. Huu-Tai P. Chau, Nucl. Phys A 773, NDL is a reference library of evaluated SPN contribute to the excellence of 56 (2006). and validated nuclear data, recom- French institutional research at 22. S. Hilaire, S. Goriely, Nucl. Phys. A mended for use in fusion and fission large, and to the scientific credibility 779, 63 (2006). applications. In the most recent JEFF of the CEA DAM programs in par- 23. http://www.talys.eu 24. H. Duarte, Phys. Rev. C75, 024611 3.1 neutronic library released in 2006, ticular. out of 381 isotopes, SPN has contrib- (2007). uted to 8 (n + 103Rh, 127,129I, 236,237,238U 25. M.J. Lopez-Jimenez, B. Morillon, P. Romain, Ann. Nucl. Energy 32, 195 and 239,240Pu). For the coming JEFF 3.2 References (2005). library, more isotopes are prepared in 1. http://www.efnudat.eu 26. M.B. Chadwick et al., Nucl. Data collaboration with CEA DEN Cadarache 2. I. Lantuéjoul, PhD Thesis, University Sheets 108, 2742 (2007). and NRG Petten. of Caen (2004). In parallel, a significant effort has 3. A.A. Bergman and al. Proceedings of ERIC BAUGE been devoted to the new JEFF3.1.1 the First International Conference on Bruyères-le-Châtel

12 Nuclear Physics News, Vol. 18, No. 4, 2008 feature article

Deep Underground Laboratories—Somewhere Quiet in the Universe

NEIL SPOONER University of Sheffield, ILIAS, LAGUNA, and Boulby Laboratory Q1

Introduction: Nobel and Noble Dreams Notable among the latter is work on so-called Dark Life, The world’s very deep underground laboratories offer the search to understand the origins of the microbial life access to the ultimate in quiet environments for science found in abundance in deep rock. Around 50% of the research. Here the term quiet generally refers to the cosmic- world’s total biomass is underground. Dark Life aside, ray muon flux that is greatly reduced in these laboratories DUSEL, if given the final go-ahead by the U.S. Congress, compared to that at the surface. It is this feature that allows is hugely exciting for nuclear and particle astrophysics, observation or searches for very rare fundamental physics providing opportunities for the United States to contribute processes, impossible to undertake on the surface because better to the growing range of large, next generation experi- of the muon-induced background. Perhaps most notable of ments being developed at European sites and in Asia. these is solar neutrino physics, for which, after a long his- Among these is a growing enthusiasm for the use of liquid tory, Ray Davies received in 2002 with Masatoshi Koshiba noble gas technology, argon, neon, and xenon, as possibly the Nobel prize for measurement of neutrinos from the Sun. the next great detector technology (see Figure 1). Such work falls firmly within the field of Particle Astrophysics—the use of particle physics to study astro- The World’s Deep Laboratories—Deep and Dirty physics and of astrophysics to study particles. However, in To put this in context, shown in Table 1 is a compen- the underground world quiet increasingly means also low dium comparing vital characteristics of the world’s current vibration noise, low electrical noise, low natural radiation, and up-coming most well-known deep underground sites low radon gas, and even low biological contamination. and in Table 2 an overview of the experimental activity and Realization of this, and that for particle physics the next big status of expansion plans, where known (see also Ref. [2] energy frontiers may in fact more economically be reached and related sources). The first characteristic generally of via new opportunities underground than at accelerators, is interest to users is the depth (Table 1, column 4) because starting to generate a revolution of development. Large new this is related to the level of cosmic-ray shielding provided experiments are planned, many laboratories are pushing by the rock. Traditionally, this is given in m.w.e. (meters expansion schemes, and new deep laboratories are being water equivalent), the depth normalized to the density of built. The discipline once termed Underground Particle water (to allow for different rock types). However, great Astrophysics and devoted mainly to solar neutrinos is trans- caution is needed with m.w.e. because this may refer just to forming into a diverse field, itself becoming a sub-topic of the vertical depth above the laboratory which, for a mine a new interdisciplinary field called simply Underground site in particular, tends to underestimate the relative shield- Science. ing, because most lines of sight from the laboratory to the This renaissance is perhaps best exemplified by the surface pass through a greater thickness of rock than that of enthusiasm for construction in the United States of a hugely the vertical depth. A better comparison for most purposes, ambitious new national laboratory, the Deep Underground which naturally accounts for the averaging of the rock Science and Engineering Laboratory (DUSEL) [1]. After cover, is to use the actual measured muon flux (also in col- an intense competition over several years the location of the umn 4). This also accounts for the slight effect of different £0.5B DUSEL was chosen in April 2007 to be the disused latitudes and altitudes. It should be noted here that there are Homestake Gold Mine in South Dakota. The laboratory has a much larger number of underground laboratories at shal- already attracted interest as a site for around 100 experi- lower depth not shown here, for instance as covered in ments, split between particle astrophysics and a range of new Europe by the organization CELLAR [3]. These sites, in science that includes significant microbiology interests. general less than 200-m deep, undertake, for instance, low

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laboratories. In particular, the need to cooperate closely with the host owners, the public road authorities, mine company, national park, or other bodies that all impose constraints. These economic and ownership factors have partly limited both the number of sites and their scope for expansion, resulting in a significant lack of deep space for science, particular at greater depths. Recognizing this, there has been a trend in recent years toward better coordination between laboratories, to exchange best practice and experience to improve efficiency for the user, but also toward coordi- nated, more efficient, allocation of space. The aim being to site experiments at the laboratories best suited to their scientific needs rather than for geographical reasons. A particular case is dark matter experiments searching for Weakly Interacting Massive Particles. As the need to probe to ever- lower cross-sections increases, so does the need for greater depth, to reduce further the muon-induced neutron background. Some priority will be needed to move next generation dark matter experiments to sites with the necessary depth, while other classes of experiment proposed, for instance for proton decay using liquid argon like GLA- CIER, can function comfortably at shallower sites [5]. Coordination between laboratories is exemplified in Europe by the highly successful new organization ILIAS (Integrated Large Infrastructures for Astroparticle Science) [6]. Set up in 2003 and funded by the European Union, ILIAS has brought together the four main deep laboratories in Europe—Boulby, Canfranc, Frejus, and Gran Sasso. ILIAS involves over 20 institutes representing around 1,500 scientists with interest in underground physics and gravitational waves. ILIAS is run through a set of six networks, three joint research projects, and a Trans-national Access Figure 1. The first ton-scale dark matter detector, ArDM, Programme (TA). Particular success has been production of uses liquid argon—seen here undergoing tests at CERN [2]. the first databases collecting together information on low background materials and techniques produced by the laboratories [6]. A specific laboratory network has produced joint background measurements of materials but are not involved safety training and policy activity and, through regular meet- in front-line fundamental research. ings between the directors, progress toward coordinating sci- Perhaps unique to the deep laboratories (see Table 1), is ence policy. The TA underpins much of ILIAS, providing a the significant range of characteristics that reflect not just the jointly run fund to which groups can apply for resources to requirements of the science but the severe constraints gain access to any of the laboratories. imposed by geographic and local economic factors required for establishing a deep underground site. This arises because underground science alone has not so far provided sufficient Important Comparative Features—Rock justification to fund the necessary access excavation. Rather, and a Hard Place almost all sites piggyback off an existing underground infra- Comparing again the characteristics of the laboratories structure, usually a public road tunnel or deep mine. This sit- (Table 1), several particular features and their interaction uation introduces other peculiarities and challenges for the with the science are worth noting.

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Table 1. Summary characteristics of the world’s deep underground laboratories.

Depth and muon Rock and Site Location and access Current space flux (m m-2 s-1) radon (Bq m-3) Neutrons (m-2 s-1)

Europe BNO Andyrchi, Russia; 3 halls: 24 × 24 × 16 m3; 850 m.w.e. and 4,700 40 norite rock 1.4 × 10−3 (>1 MeV); independent tunnel 60 × 10 × 12 m3; m.w.e. (SAGE area); 6.28 × 10−4 (>3 MeV) 40,000 m3 3.03 ± 0.19 × 10−5 BUL Boulby mine, UK; 1,500 m2 2,800 m.w.e. under flat 1–5 salt 1.7 × 10−2 (>0.5 MeV) vertical surface; 4.5 ± 0.1 × 10−4 CUPP Pyhasalmi mine, >1000 m2 spaces no longer down to 1,400 m — pyrite ore, — Finland; vertical used by the mine zinc ore × −2 LNGS Gran Sasso, Italy; 3 halls plus tunnels total 3,200 m.w.e., under 50–120 CaCO3 3.78 10 (total); 2 × −4 × −2 road tunnel 17,300 m ; mountain; 3 10 and MgCO3 0.32 10 180,000 m3 (>2.5 MeV) LSC Canfranc, Spain; 2 halls: 40 × 15 × 12 m3; 2,400 m.w.e., 50–80 limestone, 2 × 10−2 road tunnel 15 × 10 × 8m3; under mountain; tot 1,000 m2 2 × 10−3–4 × 10−3 LSM Modane, France; 1 hall and service 4,800 m.w.e. under 15; (0.01 filtered) 5.6 × 10−2 (work road tunnel areas: 400 m2 mountain; 4.7 × 10−5 calcitic schists in progress) SLANIC Prahova mine, 70,000 m2 average 208 m, under flat surface 6 salt — Romania; vertical ht. 52–57 m SUNLAB Sieroszowice mine, 85 × 15 × 20 m3 900–950 m (2200 m.w.e.) 20 salt and — Poland; vertical 650–700 m for large copper ore caverns SUL (Uk) Solotwina mine, 25 × 18 × 8m3; 1,000 m.w.e. under flat 33 salt <2.7 × 10−2 Ukraine; vertical 4 of 6 × 6 × 3m3; surface; 1.7 × 10−2 total area 1,000 m2

Asia INO (proposed) Masinagudi, India; 2 halls: 26 × 135 × 25 m3; 3500 m.w.e. — compacted — independent tunnel 53 × 12 × 9m3 granite Kamioka Japan; independent Hall SK 50 m dia; 40 × 4 2700 m.w.e. 3 × 10−3 20–60 lead and 8.25 ± 0.58 × 10−2 (th); horizontal and 100 × 4m wuth L-arm zinc ore 11.5 ± 1.2 × 10−2 (fast) Oto-cosmo Tentsuji, Japan; 2 halls: 50 m2; 33 m2; 1400 m.w.e. 4 × 10−3 10 (radon 4 × 10−2 Indep. horizontal total ~100 m2 reduced)— Y2L YangYang, S. Korea; Current space: 100 m2 ~2000 m.w.e. 2.7 × 10−3 40–150— 8 × 10−3 (1.5–6.0 MeV) horizontal Planned space: 800 m2

North America DUSEL Homestake, USA; 7,200, 4,500, 100 m2 at 1,450, 233, 4,100, 6,400, 7,000 ~40–200 (at 1478 m) — (proposed) vertical 2,200, 2,438 m dep m.w.e. under flat surface metasedimentary SNOLAB Creighton mine, SNO ~200 m2; main 6,001 m.w.e. under flat 120; norite, 4.7 × 10−2 (th) Canada; vertical 18 × 15 × 15–19.5 m3; surface 3 × 10−6 granite gabbro 4.6 × 10−2 (fast) ladders 6–7 m; total 46,648 m3 SUL (US) Soudan mine, USA;~ 2 halls: 72 × 14 × 14 m; 2,000 m.w.e under flat 300–700; Ely 2 × 10−2 (calc) vertical 82 × 16 × 14 m; tot 2,300 m2 surface 2 × 10−3 greenstone WIPP Carlsbad, USA; 500 × 8 × 6 m available 2,000 m.w.e. 2 × 10−3 <7; salt 115+/−22 m−2d−1 vertical expected (th + ath) Kimballton Butt Mountain, USA; 30 × 11 × 6 m 1,400 m.w.e — Paleozoic — horizontal dolomite

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Table 2. Deep undeground experiments and plans.

Site Users (approx.) Current experiments Future plans

Europe BNO Staff 50–60; Neutrinos: BUST; SAGE Uncertain Users 30–35 BUL Staff 2; Dark Matter: ZEPLIN II, ZEPLIN III, DRIFT II; Expansion to deeper hard rock Users 30 Other: SKY, ongoing R&D, HPGe measurements, underway; LAGUNA geophysics CUPP Staff 3–6; Muons: EMMA Expansion study; LAGUNA Users 10 LNGS Staff: 64 + 23 Dark matter: LIBRA, CRESST2, XENON10, WARP; MODULAr—New facility Users: 750 Double Beta Decay: COBRA, CUORICINO, at shallow depth GERDA; Solar/geo/SN/beam neutrinos: (1,200 m.w.e.) proposed BOREXINO, LVD, OPERA, ICARUS; Nuclear astrophysics: LUNA2; Other: VIP, LISA, R&D, HPGe, geology, biology, environmental studies LSC Being defined Being defined by open call. In old lab: ANAIS, LAGUNA Rosebud, R&D activity, 4 HPGe detectors LSM Staff 8–9; Dark Matter: EDELWEISS; Double beta Decay: ULISSE: 2 new halls: 100 × 24 m; Users 100 NEMO, BiPo, TGV; Other: SHIN, HPGe detectors 18 × 50 m (with water shield). MEMPHIS, LAGUNA 116 SUL (Uk) Staff 14; Double Beta Decay: CdWO4 scintillators, Uncertain + Users 11 SuperNEMO R&D; R&D on: CaWO4, ZnWO4, PbWO4, CaMoO4, new molybdates SLANIC Variable MicroBq laboratory and whole body counting HPGe spectrometry; nuclear astrophysics; LAGUNA SUNLAB Being defined Being defined LAGUNA

Asia INO (proposed) Staff: 50–100 ICAL—50 kt magnetized Fe tracking calorimeter for Plans being prepared atmospheric and very long base-line accelerator neutrinos Kamioka Staff: 13 + 2 Neutrino astrohysics and beam: Super-Kamiokande, New halls: 15 × 21 m for XMASS Users: >200 XMASS prototype, KAMLAND; Dark Matter: 800 kg; 6 × 11 m for CANDLE; NEWAGE, XMASS; Gravity: CLIO; Double Beta gravitational antenna LCGT Decay (proposed): CANDLE. request; Hyper-K study Oto-cosmo Users: ~20 Double Beta Decay, Dark Matter: ELEGANTV, uncertain

MOON-1, CaF2 Y2L Users: ~30 Dark Matter: KIMS; Double Beta Decay R&D; HPGe Can be expanded as desired

North America DUSEL Staff: >80 First experiments through SUSEL Inc. LUX (Dark Expansion depends on approval (proposed) Users: >200 Matter) SNOLAB Staff: ~30 Neutrino astrophysics/Double Beta Decay: SNO+; SuperCDMS, EXO. Further Users: >100 Dark Matter: DEAP/CLEAN, PICASSO; Letters site expansion limited being considered by rock removal SUL (US) Staff: 9 Neutrino beam: MINOS; Dark Matter: CDMS II; low Uncertain Users: >200 background WIPP Staff: as needed Double Beta Decay R&D: EXO, MEGA/SEGA, Expansion to fill designated area MAJORANA Kimballton Staff: as needed Neutrino astrophysics: LENS, R&D Expansion to fill designated area

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The Rock The geology of a site is of course a critical factor. First, it determines the natural radiation background, both gamma, principally from the U, Th, and K levels in the rock, and the neutron background, from rock fission and muons [7]. These backgrounds are critical for most particle astrophysics experiments and require expensive passive or active shielding techniques, the design of which, principally the thickness and hence the cost, depend on this background. Extreme examples of note are sites in salt, such as WIPP, Boulby, and Slanic, for which the natural rock background can be exceptionally low. In harder granite-type rock, the background can be higher by 100 times or more. Although the background gamma flux is straightforward to measure, using a Ge detector for instance, it is much more Figure 2. The Slanic site in Romania—a relatively shallow challenging to determine the ambient fission and muon site but with exceptionally large caverns excavated in salt. neutron background. New measurement techniques are being developed for this, for instance at Boulby and Modane [7,8]. Interestingly, these confirm simulations Creighton mine currently holds the record for the largest sin- showing that although salt provides a gamma background gle cavity at depth. significantly improved over other rock forms, the scattering process for neutrons in salt means the neutron background Tunnel versus Mine is not improved by nearly the same factor. One striking difference between the sites for the user is The uranium content of the rock, together with the geol- the division between tunnel-based and mine-based sites. ogy, porosity, and the ventilation characteristics, also criti- The advantages held by the former are often cited, for cally determine the radon levels. Contamination by radon instance the benefits of horizontal access, such as at and its daughters is a major issue for many experiments Modane and Gran Sasso. Meanwhile, a key disadvantage of with widely different concentrations encountered in the dif- a mine site is often stated to be the dependency on the mine ferent sites. Again salt wins here with levels typically of a owners, particularly the implications of cessation of min- few Bqm−3, compared to 100–1,000 times more in some ing. However, while horizontal access may be an advantage other sites (see Table 1). Nevertheless, all sites need to take during experiment construction, allowing large single loads precautions. At Modane for instance, a dedicated radon to be delivered by lorry, for the individual user vertical, reduction plant has been pioneered that uses an array of walk-in, lift access, direct from a nearby surface facility, cooled carbon filters [8]. Such plants will need to feature in can be more convenient. Meanwhile, mine companies, such new excavations seeking the lowest backgrounds. as INCO at SNOLAB or CPL at Boulby, are anyway well The rock type, in combination with the depth, seismic used to transport large items down shafts and fabricating activity, faulting, water ingress, and other geology, obviously underground—a process that can also allow better control also determines the form of cavern that can be constructed, of cleanliness for an experiment. most notably the maximum safe height. Salt, for instance, Although it is clear that good relations are needed with undergoes plastic flow at depth, which restricts the excava- mine owners for those sites, it is also the case that road tun- tions (without significant extra support) to heights perhaps nel sites are at the mercy of the relevant tunnel authorities. <15 m, as at Boulby. Here, though, the length of excavation One concern is safety. This is a key matter in both cases but is essentially unlimited. However, at shallower depths, such particularly for tunnel authorities because of the presence as Slanic, this restriction relaxes. Here extraordinary caverns nearby of the general public, an increasing issue for tunnels of 40–50 m in height have been in use for many decades highlighted in the Alpine sites by several recent fires. The (Figure 2). To create larger caverns at depth, harder rock, advantage at a mine is that access for all personal is strictly such as at Gran Sasso, is essential, although again depth is an controlled, there is no presence of mass general public issue as the rock pressure increases. The SNO cavity at nearby to consider, specific safety and evacuation training

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and the potential lack of a collegiate social atmosphere away from home institutions. These are challenges for the laboratory directors but arguably worse in some cases are the environmental challenges, particularly in Europe now, where all four deep sites are in national parks. This has, for instance, restricted surface laboratory development at Boulby and at Gran Sasso has halted expansion plans in part due to the environmental impact on the local water table. All site developments increasingly need to take account of environmental impacts. More importantly, site location is vital to certain science activity, notably neutrino physics. Here, if the best neutrino oscillation physics is to be extracted then the distance to a potential next-generation neutrino beam or factory needs to Figure 3. Inside the Borexino detector at Gran Sasso. be optimized, depending on the beam energy. Long base- lines favor better separation of matter effects from CP violation and provide a richer neutrino physics, including θ can be made compulsory for all, changed and improved as determining the MNSP matrix elements, especially 13 [9]. needed and the location of everyone can be monitored and This factor has, for instance, been an issue for Soudan, being controlled. Any incident can therefore be contained more rather too close to Fermilab (724 km) and conversely pro- quickly and is likely to have fewer repercussions. vided encouragement for the development of Phyasalmi, This degree of available control makes mine sites possi- where the distance to CERN (2,300 km) makes this attrac- bly also more suitable for future experiments requiring tive. Conversely, the proximity of Frejus to CERN (130km) unusual or potentially dangerous materials, such as, for may disfavor this site. This matter was a consideration for instance, large volumes of cryogenic gases or low flash- DUSEL where the chosen site of Homestake is at 1,290km point scintillators. The flexibility of mine sites through from Fermilab and 2,540km from BNL. The relative remote- direct access on-site to excavation machinery and mining ness of a site like Phyasalmi or SNOLAB, away from com- engineers, is a further advantage here. It allows existing mercial nuclear energy reactors is also a consideration. The caverns to be adapted or new ones built quickly if neces- anti-neutrino background from these is, for instance, a limit- sary, whereas for tunnels, once the road or dam building ing factor for new experiments seeking to observe the back- has been completed, major changes are problematic except ground neutrino flux from past supernova, while in the new in special circumstance. This ready prospect for new exca- field of geo-neutrinos location in relation to the local thick- vation also opens advantages for interdisciplinary science, ness of the Earth’s crust is an issue [10]. notably access to fresh, uncontaminated rock. This is key for potential microbiology applications and in geophysics and engineering projects, such as waste management stud- Science and Expansion—Hooray for Proton Decay ies. Finally, no existing tunnel site can provide access to the There has been outstanding success recently in under- great depth needed by many upcoming physics experi- ground physics, most obviously in solving the solar neutrino ments, at least not without excavating a vertical shaft! problem, with SNO at SNOLAB, at SuperK and Gran Sasso, but also with neutrino beam experiments, and in dark matter Geographic Location and double beta decay, where it has proved possible to build A final point worth highlighting here are issues arising ever larger and more sophisticated experiments underground. from geographic location. Through the dependency on a Table 2 lists most of the current activity. The recent success deep mine or mountain range to provide the over-burden, of Borexino at Gran Sasso (see Figure 3) is a particular mile- all current deep laboratories are located in relatively stone, not just for successfully observing 7Be solar neutrinos remote, rural areas. This introduces extra challenges for the in real time but because this experiment has demonstrated the user, notably from the limited transportation options, feasibility of achieving backgrounds in a large (87.9 ton, lengthy travel times, the limited nearby accommodation, fiducial) active medium, liquid scintillator in this case, at the

18 Nuclear Physics News, Vol. 18, No. 4, 2008 feature article

exceptional level of 7×10−18 g/g 323Th—a value once >3000 m2, made possible by the highway agency’s need to thought impossible [11]. This progress, together with rapid excavate a new emergency evacuation tunnel. One of these development of new technologies, such as very large liquid halls is proposed to have an integrated water shield to pro- noble gas detectors, notably liquid argon, plus better under- vide the ultimate low background room, possibly the quiet- standing of how to build large caverns at depth, points the est place in the Universe [8]! way to a far more ambitious future. All the LAGUNA sites in fact have general expansion The pinnacle here would be construction of a 100– plans. At Boulby for instance, the mine company is proceed- 1,000 Kton experiment (~20 times SuperK) that would push ing into new deeper hard rock areas with new science labora- proton decay sensitivity by one to two orders, including in tories to be made available, starting with a dedicated the kaon channels [5]. However, such a detector could also geophysics laboratory. At Phyasalmi, now the deepest mine measure the relic neutrino flux from past supernovae for the in Europe at 1400m, engineers are proposing a new facility first time; observe neutrino bursts from new supernovae; separated from the main mining activity. Perhaps the best- geo-neutrinos and, with a suitable beam, unravel lepton CP known expansion activities are at SNOLAB and DUSEL. θ violation and measure 13 to exceptional precision. In The Canadian site is nearing completion of an exceptional Europe the LAGUNA collaboration, now partly funded by facility that includes the first purpose-built underground lab- the European Commission, will study three potential tech- oratory for experiments using cryogenic liquids, the Cryopit nologies—water cherenkov, liquid argon, and liquid scintil- Laboratory (see Figure 4). In the United States, although lator—and investigate options for an underground site. Six DUSEL, as the world’s largest currently planned new site, are being considered—Boulby (UK), Canfranc (Spain), will need final congressional approval, the first stage is pro- Frejus (France), Phyasalmi (Finland), Slanic (Romania), ceeding anyway thanks to state donations and funds from and Sunlab (Poland) (see Table 2). Work has started with local philanthropist Mr. T. Denny Sanford (SUSEL). This engineers and companies to determine the safe size and will see rapid restoration of the original cavern at Homestake form of caverns that could be built at each site. used by Ray Davis to make his detection of neutrinos from LAGUNA is Europe’s answer to similar megaton activ- the Sun—a fitting tribute to his pioneering work in one of the ity in Asia and North American. DUSEL at Homestake original Deep Underground Laboratories. would now be the location for a U.S. version. In Japan, plans for HyperK are well advanced with detailed rock Acknowledgments studies in the region of Kamioka mine already completed The author thanks ILIAS (contract no. RII3-CT-2004- [12]. However, in this region there is potential interest in a 506222) and CPL (Boulby) and LAGUNA for support. large detector further downstream from the Tokai neutrino beam as part of extensions to the current T2K experiments. Such a detector could be lined up with SuperK and located in South Korea or, as recently proposed, on the Japanese island of Okinoshima [13]. Although likely costing a fraction of CERN’s LHC, the scale of a nucleon decay facility means probably only one site will ever see such an experiment. However, the vibrancy in underground science in general is seeing growth now anyway, with new sites emerging, such as the recently funded Indian Neutrino Observatory (INO), and many expansions underway (see Table 2). The drive for much of this is new dark matter and neutrino experiments, including for double beta decay. These fields are maturing and now developing a new generation of larger, multi-ton, experiments with more sophisticated background reduction. In Europe, the new Canfranc halls have recently been Figure 4. Schematic plan of the new SNOLAB expansions built with this in mind and at Frejus, the deepest in Europe, showing the SNO cavern (left), new laboratories (blue), and ULISSE is well advanced to establish two new halls totalling further extension for the Cryopit laboratory (top right).

Vol. 18, No. 4, 2008, Nuclear Physics News 19 feature article

References 1. www.lbl.gov/nsd/homestake/ 2. L. Kaufmann et al., Nucl. Phys. B—Proc. Supp. 173 (2007), 141. 3. A. Bettini, Proc. TAUP2007, www.iop.org/EJ/volume/ 1742-6596/120/8 Q2 4. M. Laubenstein et al., App. Rad. & Isotopes 61 (2004), 167. 5. J. Aysto et al., JCAP 0711 (2007), 011. 6. www-ilias.cea.fr 7. E. Tziaferi et al., Astroparticle Phys. 27 (2007), 326. 8. www-lsm.in2p3.fr/ 9. V. Barger et al., arxiv.org/abs/0705.4396 10. A. Kathrin et al., Astroparticle Phys. 27 (2007), 21. 11. C. Arpesella et al., Phys. Lett. B 658 (2008), 101. 12. N. Wakabayashi, proc. NNN07, www-rccn.icrr.u-tokyo.ac.jp/ NNN07 13. A. Rubbia et al., arXiv:0804.2111.

NEIL SPOONER University of Sheffield and Boulby Laboratory

20 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods

JUSTIPEN—The Japan U.S. Theory Institute for Physics with Exotic Nuclei

International collaborations fill These questions align well with the activity between the United States and today’s research landscape, facilitate drivers of rare isotope science. One Japan would benefit both countries in scientific progress, and lead to a stron- primary aspect of the first and second this area of science. The U.S. contri- ger scientific community through questions concerns testing the predic- bution through the U.S. Department of tackling mutually beneficial research tive power of models by extending Energy JUSTIPEN grant provides problems. Furthermore, international experiments to new regions of mass travel and local support for U.S. scien- research collaborations result in a cul- and proton-to-neutron ratio and identi- tists to visit scientists in Japan tural understanding among the com- fying new phenomena that will chal- involved in the study of nuclei. Mean- munity of scientists. For these general lenge existing many-body theory. while, the University of Tokyo (abbre- reasons, the Japan U.S. Theory Insti- In order to achieve the overarching viated as Todai in Japanese) and tute for Physics with Exotic Nuclei goal of a comprehensive description RIKEN have established the Todai- (JUSTIPEN) was established two of all nuclei, a new generation of rare RIKEN Joint International Program years ago. JUSTIPEN enables travel isotope facilities is coming on-line to for Nuclear Physics (TORIJIN) in of U.S. scientists to Japan to collabo- produce very short-lived nuclear spe- order to enhance jointly international rate with their Japanese counterparts cies in the laboratory. Notable among collaborations and exchanges in as the community pursues a basic these new facilities are the Rare Iso- nuclear physics, and the University of understanding of exotic nuclei and tope Beam Factory at RIKEN in Tokyo has created an associate profes- their role in astrophysics and other Japan, which began operations in sor position designated for this pur- areas. In this brief report, I will November 2006, the Facility for Anti- pose. One of the major purposes of describe the activities of JUSTIPEN proton and Ion Research (FAIR) facil- TORIJIN is obviously to host the during the last two years. ity at GSI which is under construction, JUSTIPEN activities including the Experimental and theoretical stud- and isotope separation techniques, JUSTIPEN office in the RIBF build- ies are now underway to attain a which continue to be developed at ing of the RIKEN Nishina Center and deeper understanding, richness, and SPIRAL-II, Ganil in France, and TRI- various cares for JUSTIPEN visitors. diversity of nuclear phenomena. Key UMF in Canada. These new facilities, While this office is the hub of JUSTI- scientific themes that are being in addition to existing experimental PEN activities, we also provide sup- addressed are captured by five over- efforts at premier facilities such as the port for travel to other Japanese arching questions that have been National Superconducting Cyclotron venues for collaborative research. developed during the last few years. Laboratory at Michigan State Univer- Detailed information on JUSTIPEN These are: sity and the Holifield Radioactive Ion can be found at the Web page Beam Facility (HRIBF) at Oak Ridge www.phys.utk.edu/JUSTIPEN. This • What is the nature of the nuclear National Laboratory (ORNL), and website provides a repository of infor- force that binds protons and neu- including the proposed Facility for mation for JUSTIPEN including visi- trons into stable nuclei and rare Rare Isotope Beams (FRIB) in the tor information, exit reports, detailed isotopes? United States, hold the key to unlock- information on how to function at • What is the origin of simple pat- ing the mystery of nuclei and nuclear RIKEN, JUSTIPEN policies, and terns in complex nuclei? production in the universe. other items. • What is the nature of neutron stars Theoretical investigations of nuclei and dense nuclear matter? and their applications will also benefit • What is the origin of the elements from experiments at current and new JUSTIPEN Opening, in the cosmos? facilities, and a group of Japanese and July 10–11, 2006 • What are the nuclear reactions that U.S. scientists realized that an JUSTIPEN was opened during drive stars and stellar explosions? enhanced theoretical collaborative mid-July, 2006. Members of the U.S.

Vol. 18, No. 3, 2008, Nuclear Physics News 21 facilities and methods

team on this trip included Steering During its first year of opera- JUSTIPEN, called for short as Committee members Witek Nazare- tions, JUSTIPEN provided funding JUSTIPEN-U.S. hereafter. wicz (University of Tennessee), Baha to 10 U.S. visitors and to approxi- The EFES initiative resulted in an Balantekin (University of Wisconsin), mately 25 visitors during its second exchange activity in March 2007. The Richard Casten (Yale University), and year. first Joint JUSTIPEN-LACM Meeting David Dean (ORNL), as well as Sidney was held at the Joint Institute for Coon (U.S. Department of Energy Heavy Ion Research (JIHIR) at ORNL Office of Nuclear Physics Theory Pro- JUSTIPEN-U.S. from March 5–8, 2007. The meeting gram Manager), and Bruce Barrett (U. During this time, Japanese col- was a merger of two workshops: Arizona, and one of the initial long-term leagues also worked toward estab- (1) the annual National Nuclear Secu- visitors to the Institute). Also attending lishing funding opportunities to send rity Administration–Joint Institute for the meetings were many Japanese col- Japanese to the United States for Heavy Ion Research (NNSA–JIHIR) leagues; a partial list is given with the collaborations. This effort brought meeting on the nuclear large ampli- official picture of the opening, shown in them with the “International tude collective motion (LACM) with Figure 1. During July 10, talks were Research Network for Exotic Femto an emphasis on fission, and (2) the given to explore what kinds of scientific Systems (EFES)” as a Core-to-Core U.S.–Japan theory meeting under the collaborations could come from the project by the Japan Society for the auspices of JUSTIPEN. The purpose Institute. Numerous ideas were put for- Promotion of Science (JSPS). The of the meeting, jointly organized by ward for the JUSTIPEN efforts. Policy EFES project played major strong the JUSTIPEN Governing Board, by was also discussed at the meeting. roles as Japanese matching fund to the UT/ORNL nuclear theory group, and by the EFES, was to bring together scientists (theorists and experimentalists) with interests in physics of radioactive nuclei, LACM, and theoretical approaches related to the Scientific Discovery through Advanced Computting (Sci- DAC) Universal Nuclear Energy Density Functional (UNEDF) project (see Figure 2). The meeting consisted of approximately 50 talks on physics of radioactive nuclei. Figure 2 includes local organizers of the workshop and the Japanese colleagues. The Tandem of the Holif- ield Radioactive Ion Beam Facility Figure 1. JUSTIPEN OPENING (L to R): N. Itagaki (University of Tokyo, (HRIBF) at ORNL stands in the secretary of JUSTIPEN); H. Sakai (University of Tokyo, JUSTIPEN governing background. board); T. Motobayashi (RIKEN, JUSTIPEN Associate Director); W. Nazarewicz The success of the 2007 meeting (University of Tennessee and ORNL, JUSTIPEN governing board); Y. Doi, led to a second meeting during 2008. (Executive Director of RIKEN); R. Casten (Yale University, JUSTIPEN The second LACM-EFES-JUSTIPEN Governing Board); B. Barrett (U. Arizona, first long-term visitor of Workshop was held during January JUSTIPEN); D. Dean (ORNL, JUSTIPEN Associate Director); B. Balantekin 23–25, 2008, at ORNL. The workshop (U. Wisconsin, JUSTIPEN governing board); S. Coon (U.S. DOE Office of program covered a number of topics Science, Office of Nuclear Physics); A. Arima (President, Japan Science including fission/fusion and other Foundation); Y. Yano (Director, Nishina Center for Accelerator Sciences, forms of large-amplitude collective RIKEN); T. Otsuka (U. Tokyo, JUSTIPEN Managing Director); M. Ishiara motion, computational nuclear struc- (RIKEN); and Y. Okuizumi (RIKEN, head of Nishina Center Administration). ture physics, nuclear structure relevant

22 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods

to nuclear astrophysics, gamma-ray some of the aspects of that research. no two-body interaction, whether spectroscopy, clustering in nuclei, and Theoretical research of the properties derived from effective field theory or topics related to ongoing and future and characteristic of nuclei necessarily from meson theory, has ever been able collaborations with Japanese groups involves coming to an understanding to simultaneously fit all nucleon- and colleagues. This meeting ran con- of the complexity of the nuclear force, nucleon scattering data, the deuteron currently with a celebration of the which involves two-body and three- binding energy, and the masses of the 25th anniversary of the building of the body (at least) interactions among triton and alpha particle. Joint Institute for Heavy Ion Research protons and neutrons, and an under- A more complete understanding (JIHIR) at ORNL. The JIHIR was the standing of how to apply quantum of the nuclear force represents an brainchild of a group of physicists, many-body theory to the nuclear prob- important avenue of research for the including University of Tennessee pro- lem. Recent advances in chiral effec- physics of nuclei. As Maria Geop- fessor (and former ORNL deputy tive field theory, using the pion and pert-Mayer said in her Nobel Lecture, director) Lee Riedinger, UT’s Carroll nucleon as the relevant degrees of “[T]he first, the basic approach, is to Bingham, and Vanderbilt University’s freedom, have connected the nuclear study the elementary particles, their Joe Hamilton, to establish a means to forces to the underlying symmetries of properties and mutual interaction. open the Lab’s Holifield Facility and QCD, and are able to accurately Thus one hopes to obtain knowledge its tools such as the Recoil Mass Spec- describe nucleon-nucleon scattering of the nuclear forces. If the forces are trometer to university users back in phase shift information. The formula- known, one should, in principle, be 1982. tion of the nuclear forces through able to calculate deductively the JUSTIPEN was the linchpin to effective field theory yields a series of properties of individual nuclei. Only obtain full funding for an expansion of Feynman diagrams with an order after this has been accomplished can the JIHIR to obtain a new “theory parameter that is a ratio of the momen- one say that one completely under- wing.” This expansion will enable a tum transfer in scattering and a stands nuclear structure” [1]. reciprocal Japanese exchange program momentum cut-off parameter, usually We certainly do understand the that will bring our Japanese colleagues taken to cover the range of scattering nuclear force better today than we did to the United States, again to benefit data up to about 500 MeV. At the third in 1965, which has led to substantial research efforts in physics with exotic order in the expansion, three-body progress in developing ab initio nuclei. Funding for this expansion will forces appear. This should come as no approaches to calculate nuclei. Pio- come from the State of Tennessee, surprise as nucleons are not point-like neering efforts using a meson-the- ORNL, the University of Tennessee, fundamental particles, but are made ory-inspired interaction, including and Vanderbilt University. Construc- up of quarks and gluons. For many three-body forces, has been carried tion began in the spring and is now years we have understood that a three- out using Greens Function Monte about 50% complete. We anticipate body force must be active in nuclei as Carlo approaches. Nuclear spectra opening the theory wing in the winter. The extension to the JIHIR will be the home-base for the JUSTIPEN-U.S. program and will consist of 4 single- person offices and 4 two-person offices.

A Brief Tour of the Physics of Exotic Nuclei Research performed through JUSTIPEN is meant to be broad and encompasses a variety of theoretical techniques (see Figure 3). In this clos- ing section, I will briefly mention Figure 2. First JUSTIPEN-LACM Meeting, March 2007.

Vol. 18, No. 4, 2008, Nuclear Physics News 23 facilities and methods

A comprehensive theory of nuclei would be incomplete without reaction theory, and progress in this arena in light nuclear systems ties nicely with efforts in ab initio calculations. Recently the Greens Function Monte Carlo collaboration calculated neutron-alpha phase shifts and found that the three-body force affects these, and No Core Shell Model group calculated 7Be(p, γ)8B cross-section as a function of center-of-mass energy. These efforts point to an interesting future for reaction theory in light nuclei. Improvements in the nuclear Figure 3. The figure shows the nuclei in the N,Z plane over layed with density functional approach should theoretical approaches being developed to understand all nuclei. also lead to a more complete description of optical potentials for nuclear scattering. are reproduced from the deuteron states, resonant states, and the non- Another line of research involves into mass 12 nuclei. Basis expansion resonant continuum) is necessary for understanding the simplicities, or methods have also produced exciting the proper description of these nuclei. symmetries, found in nuclear spectra results in light nuclei. Coupled-cluster Derivation and implementation of and relating those to the underlying techniques are being used to investigate shell-model technology to incorporate quantum many-body problem of the the nature of closed-shell nuclei into the Gamow single-particle basis states can nucleus. Numerous simplicities in Calcium and Nickel region. Although be used to describe these very weakly nuclear spectra can be described by space does not permit me to discuss bound systems and opens the door to invoking symmetry arguments. These these advances in detail, I believe we theoretical investigations of the chal- efforts will be particularly useful in have entered the era of precision lenging problems associated with open approaching neutron-rich mid-shell ab initio calculations of certain nuclei. quantum systems. Coupled-cluster the- nuclei where symmetries such as X(5) At the same time, we have wit- ory using Gamow-basis states was are believed to exist. nessed an increasing understanding of recently implemented to calculate Nuclei are produced in stars and medium mass nuclei through advances widths of and binding energies of the nuclear astrophysicists seek to under- in the nuclear shell model. Here effec- Helium isotopes. stand how nuclear processes have tive interactions derived from nuclear To reach the heavier nuclei we shaped the cosmos, from the origin of spectroscopic information in, for turn to nuclear density functional the- the elements, the evolution of stars, example, the fp-shell (with 40Ca as a ory (DFT), which utilizes both matter and the detonation of supernovae, to closed core), have enabled a wide and pairing densities to produce the structure of neutron stars and the description and codification of nuclear information on the properties of nature of matter at extreme densities. ground and excited state information. nuclei. The list of topics covered in The collaborations in this area cover Shell model calculations take on this area includes substantial research astrophysical observations and, also, various forms, including standard on the methods, the forces, extensions astrophysical simulations as nuclear diagonalization and Monte Carlo for excited states, projection to good data (and theoretical calculations) are implementations, and are widely uti- quantum numbers, fission mecha- utilized in simulations ranging from lized by experimental colleagues. nisms for heavy nuclei, and time- nucleonsynthesis to stellar explo- For those nuclei at or very near the dependent phenomena, all of which sions. Sensitivity studies indicate that neutron drip-line, inclusion of contin- are important for the development of certain nuclear processes are very uum single-particle states (scattering nuclear DFT. important for these processes and

24 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods

point to the need for experimental enhance our understanding of both nuclear astrophysics where unstable efforts on specific reaction rates. nuclei and bring a broad benefit to nuclei play an important role. both nations. The major goal of Conclusion and Perspective JUSTIPEN is to deliver an interna- In conclusion, the initial years of tional venue for research on the phys- Reference 1. M. Goeppert Mayer, in Nobel Lec- JUSTIPEN lead one to believe that the ics of nuclei during an era of tures, Physics, 1963–1970, Elsevier, exchange activity will prove to be experimental investigations on rare Amsterdam (1972), available at http:// very fruitful indeed. JUSTIPEN isotopes. We are now at the two-year nobelprize.org/nobel_prizes/physics/ affords significant opportunity for anniversary of this effort, and look laureates/1963/mayer-lecture.html U.S. and Japanese scientists to collab- forward to a continuing productive orate on numerous projects related to scientific endeavor that will enhance DAVID J. DEAN exotic nuclei. Reciprocating visits of international collaborations in the Oak Ridge National Laboratory Japanese and U.S. scientists will areas of the physics of nuclei and Oak Ridge, Tennessee, USA

Vol. 18, No. 4, 2008, Nuclear Physics News 25 facilities and methods

Compass and the Nucleon Spin Puzzle

The COMPASS Spectrometer (Ring Imaging CHerenkov) counter where Δqx()=+− [ q↓↑ () x q ↓↑ ()][ x q ↑↑ The COMPASS (COmmon Muon and by hadron calorimeters. The target ()xqx+ ↑↑ ()] are the differences of the and Proton Apparatus for Structure material is contained in two 60-cm- quark densities with quark spin antipar- and Spectroscopy) experiment has long cells, which are polarized by allel and parallel to the target nucleon been in operation at CERN since dynamic nuclear polarization in oppo- spin. The quantity x is the Bjorken vari- 2002, carrying on an ambitious exper- site directions, so that data from both able, the fraction of the nucleon momen- imental program on the spin structure spin directions are recorded at the tum carried by the target parton.

of the nucleon and on hadron spectros- same time. Since 2006, a new target Integrating g1(x) from 0 to 1 one copy. The spin structure of the magnet has been used, increasing the obtains a linear combination of the nucleon has been investigated by acceptance from ±70 mrad to three light quarks first moments + impinging a 160 GeV/c momentum m ±180 mrad. Also, the target material 1 ΔΔqqxdx= ∫ () . Using additional beam on solid polarized targets. In has been distributed in three cells, and 0 2002, 2003, 2004, and 2006 a polar- polarized as +−+ or −+−. The full information from the neutron beta- ized deuteron target (6LiD) was used, description of the spectrometer can be decay and from hyperons strangeness while in 2007 data were collected on a found in Ref. [3], whereas Figure 1 changing decay, which provide two linear combinations for ᭝q’s, (᭝u−᭝d) NH3 polarized proton target. In this gives an artistic view. Data have been article I will focus on the contribution collected both in the longitudinal tar- and (᭝u+᭝d−2᭝s), respectively, it is of COMPASS to the problem of the get mode (polarization direction paral- possible to extract ᭝Σ=᭝u+᭝d+᭝s. nucleon spin. I will not mention the lel to the beam) and in the transverse The quantity ᭝Σ can be interpreted as hadron program, searching for glue- mode (target polarization orthogonal the contribution of the quarks to the balls and exotics in central production to the beam direction). spin of the nucleon, which in general and diffractive processes, which just terms can be written as started in 2008, with a first run with a The “Spin Crisis” 190 GeV/c momentum pion beam scat- Protons and neutrons constitute 1 =+++1 ΔΣ Δ GLqG L. tering off a liquid Hydrogen target. 99.9% of the material world we live in, 2 2 A worldwide effort, both theoreti- but it is fair to say that we still lack a cal and experimental, has been full description of their internal struc- In this expression, ᭝G is the contribu- devoted to the understanding of the ture. Since the pioneering experiments tion of the gluons, and Lq,G are possi- origin of the nucleon spin during the at SLAC in the late 1960s, deep inelas- ble contributions from the gluons and past twenty years. Excellent reviews tic scattering (DIS) is the standard tech- quarks angular momenta. 1 exist on the physics case. Here I will nique to investigate the structure of the In the simple quark model the try to outline only the general terms of nucleon. Using polarized lepton beams three valence quarks are in an S-state, = the problem, giving a short account of and polarized targets the spin structure so Lq 0. There are no gluons, so that ᭝ = = our contribution. of the nucleon can be investigated. If G 0 and LG 0, thus the spin sum- The apparatus we have used for both the beam and the target spins are rule is satisfied by ᭝Σ=1. the muon beam program consists of a aligned along the direction of the inci- The first measurements of polar- two-stage magnetic spectrometer, ized electron-proton scattering were dent lepton, one structure function, g1, 60 m long, which allows the recon- can be measured from the cross-section performed at SLAC in the 1980s by struction of trajectories and momenta asymmetry of the inclusive scattering. the E80 and E130 Collaborations, and of the incoming and scattered muons In the quark parton model this structure yielded results that were consistent and of the produced hadrons. Charged function can be written as with expectations. A breakthrough particles are identified by a RICH occurred when the European Muon Collaboration (EMC) at CERN 1See, for instance, Ref. [1] for the longitudinal =⋅1 2 Δ extended these measurements to a gx1()∑ eq qx () spin; Ref. [2] for the transverse spin. 2 q much larger kinematic range, by using

26 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods

a polarized muon beam with an energy 10 times higher than at SLAC. In 1988 the Collaboration reported [4] that

᭝Σ=0.12 ± 0.09(stat) ± 0.14(syst), that is, a small value, even compatible with zero. A major surprise that soon came to be known as the “spin crisis.” Actually, the inadequacy of the static quark model should have been realized well before the execution of the EMC experiment, but very likely the major achievements of the quark model had cast a shadow on this point. Figure 1. Artistic view of the COMPASS spectrometer. In particular, the amazing success of the static quark model in explaining the magnetic moments of the baryons crisis. To single out this contribution, a the twist-two level, the transverse spin ᭝ (three valence quarks in an S-state new experimental approach was neces- distributions Tq(x) must be added to SU(6) wave-function, with Dirac mag- sary, namely semi-inclusive DIS with q(x) and to ᭝q(x) [5]. 2 ᭝ netic moment and about 340 MeV/c the identification of the hadrons in the The definition of Tq(x) is analo- mass) undoubtedly contributed to radi- current jet. A flavor tagging procedure gous to that of ᭝q(x), but it refers to cate in our minds the idea that the pro- allows us to then identify the struck transversely polarized quarks in a ton spin is carried by the quarks. parton, and thus to separately deter- transversely polarized nucleon. Since Several other polarized DIS exper- mine ᭝q,᭝q, and ᭝G. A suggestion to rotations and Lorentz boost do not iments on the proton, the deuteron, isolate the photon-gluon fusion (PGF) commute, helicity and transversity are 3 → ᭝ ᭝ and He, have confirmed the EMC process g*g qq and measure G expected to be different. Tq(x) gives result. All these experiments (includ- directly had already been put forward a a measure of the correlation between ing COMPASS) allow us now to accu- few years before, and implied measur- the transverse quark spin and the rately determine ᭝Σ, the contribution ing the cross-section asymmetry of transverse nucleon spin. Being chiral- of both valence and sea quark spins to open charm production in DIS. A new odd, transversity cannot be measured the nucleon spin, to be only 30%. experiment, with full hadron identifica- in inclusive DIS (the hard process ᭝ Actually, g1(x) and q(x) are also tion and calorimetry, therefore seemed conserves chirality) but only in a pro- functions of Q2, the square of the mass to be necessary, and COMPASS was cess in which it combines with another of the virtual photon that is exchanged proposed to CERN in 1996. chiral-odd quantity. in the process, and G(x, Q2) and Transversity can be extracted from ᭝q(x, Q2) mix up in the evolution measurements of single-spin asymme- equations of QCD, so that the extrac- The Case for Transversity tries in cross-sections for semi-inclusive tion of the first moments requires a In parallel to the necessity of direct DIS (SIDIS) of leptons on trans- full QCD fit. However, it was already measurements of ᭝G/G, semi-inclusive versely polarized nucleons, in which clear in the mid-1990s that a better DIS seemed to be the best tool to hadrons are also detected in the final understanding of the nucleon spin investigate transverse spin phenom- state. In this process the second chiral- structure demanded separate measure- ena. As a matter of fact, the knowl- odd object is the fragmentation func- ments of the missing contributions, edge of the helicity distributions tion. It was conjectured in 1993 [6] that is, the gluon polarization ᭝G/G ᭝q(x) and ᭝G does not exhaust the that there could be a correlation and Lz. In particular, several theoreti- spin structure of the nucleon. It had between the spin of a transversely cal analyses suggested a large contri- been realized in 1991 that to fully spec- polarized quark and the kT of the had- bution ᭝G as a solution to the spin ify the quark structure of the nucleon at ron into which the quark fragments.

Vol. 18, No. 4, 2008, Nuclear Physics News 27 facilities and methods

This part of the fragmentation func- The Sivers distribution function, dinal target polarization mode (from the ᭝T tion is usually named Collins function 0q(x) [7], is probably the most flavor separated helicity distributions, to ᭝0 h (T Dq ). In the hadronization of a famous TMD distribution function. L-physics and to vector meson-physics). transversely polarized quark a non- Allowing for a correlation between the To directly measure ᭝G two pro- zero Collins function would be nucleon spin and the intrinsic KT of the cedures have been followed to tag the responsible for a left–right asymmetry quark, the distribution of the hadrons PGF process. The first one consists in of the hadrons with respect to the resulting from the quark fragmentation selecting open-charm events, which plane defined by the quark spin and might exhibit a left–right asymmetry provide the purest sample of PGF momentum directions. In SIDIS on a (usually called the “Sivers asymmetry” events, but at a low rate. Open-charm

transversely polarized nucleon, a non- ASiv) with respect to the plane defined events are identified by reconstructing ᭝0 h ᭝ 0 0 + − zero T Dq , in conjunction with Tq, by the nucleon spin and the virtual pho- D , D , D* and D* mesons from would cause a left–right asymmetry of ton direction. In this case the observable their decay products. The full 2002– the resulting hadrons with respect to is the product of the Sivers DF and the 2006 data set has been analyzed and the plane defined by the struck quark FF. Measuring SIDIS on a transversely the preliminary results are given in spin (i.e., the nucleon spin, reflected polarized target allows the Collins and Table 1, where m2 is the QCD scale. about the normal to the scattering the Sivers effects to be disentangled. A second option is to select events

plane) and the virtual photon Investigation of the transverse spin with two high-pT hadrons (with direction. In this case the measurable phenomena in SIDIS is complementary respect to the virtual photon direc- asymmetry, the so-called Collins to the investigation of longitudinal spin tion), as tags of the two jets from the

asymmetry, AColl, is the convolution phenomena. A spin sum-rule can also be hadronization of the qq pair. The latter ᭝ ᭝0 h of Tq and of T Dq , and has origi- written for the transverse spin case [8] procedure provides much larger statis- nally been suggested as a possible way tics but leaves a significant fraction of to measure transversity. 1 1 background events in the selected sam- =+∑ Δ qL. The transversity distribution and 2 2 q T q ple, which has been estimated with the Collins function are two examples sophisticated MonteCarlo simulations. of correlations (quark spin and The gluon contribution being absent in DIS events (Q2 >1 (GeV/c)2) and low nucleon spin, quark spin and fragmen- the transverse case, from the knowl- Q2 events are considered separately, edge of direct information on the size tation hadron kT respectively), which and different generators are used as recently have been recognized as of the orbital angular momentum can reliable models for the interaction of being crucial for understanding the be derived. the virtual photon with the nucleons. spin structure of the nucleon in terms Results from the Q2 <1 (GeV/c)2 of the quark and gluon degrees of free- COMPASS Results on data collected in the years 2002–2003 dom of QCD. Particularly important Longitudinal Spin have already been published [9]. A are the transverse momentum depen- In this short report I will concentrate preliminary value for ᭝G has been dent (TMD) parton distribution and only on the measurements of g1 and of extracted from the whole set of 2002, fragmentation functions. These func- ᭝G/G, and will skip all the other results 2003, 2004 deuteron data, and it is tions are time-reversal odd (T-odd) COMPASS has obtained in the longitu- given in Table 1. functions, and as such are of particular importance as they can generate single-spin asymmetries. Large single- ᭝ spin asymmetries in hadron-hadron Table 1. COMPASS results for the direct measurement of G/G. collisions have been known for many Statistical Systematic ᭝ 2 years, and have been measured even Method G/G error error GeV/c recently at RHIC, and a large-scale − ± ± effort is ongoing to provide in the Open charm 0.49 0.27 0.11 0.11 13 2 + ± ± framework of QCD a unified descrip- high-pT events, Q >1 0.08 0.10 0.05 0.082 3 tion of both the SIDIS and the hadron- high-p events, Q2 <1 + 0.016 ± 0.058 ± 0.055 0.085 3 hadron transverse spin asymmetries. T

28 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods

normalization scheme and obtained for the singlet moment at Q2 =3 (GeV/c)2

᭝Σ = 0.30 ± 0.01(stat) ± 0.02(evol).

The same fit provides estimates for ᭝G(x) and for its first moment. Two different solutions are equally accept- able, one with ᭝G(x) > 0 and the other with ᭝G(x) < 0. Figure 3 shows the distributions of the gluon polarization that results from the two fits. The conclusion from the fit is that the first moment of ᭝G(x) is of the order of 0.2–0.3 in absolute value at d Figure 2. The asymmetry A 1 as measured in COMPASS [10] and previous results Q2 = 3(GeV/c)2. 2 2 from SMC [11], HERMES [12], SLAC E143 [13], and E155 [14] at Q >1 (GeV/c) . Also shown in Figure 3 are our direct measurements from Table 1, as A similar analysis has been per- photoabsorption cross-section. Using well as the published results [15] and 2 d formed for the SIDIS events (Q >1 all the available g 1 data, we have the recent preliminary value [16] from (GeV/c)2). A preliminary analysis of performed a QCD fit [10] in the MS the HERMES Collaboration, and the the data collected in 2002, 2003, and 2004 has provided the results shown in Table 1. The COMPASS experiment has also measured with high precision the longitudinal virtual photon asymmetry d A 1 of the deuteron. Figure 2 gives the COMPASS measurement, which refers to 2002, 2003, 2004 and has been recently published [10], compared with previous measurements [11–14]. At small x (x < 0.03) the COMPASS data exhibit errors that are considerably smaller than the previous SMC results, which is of great rele- vance when extrapolating the data to = x 0 to evaluate the first moment of g1. d d From A 1 the structure function g 1 of the deuteron is obtained

F d gd = 2 Ad 1 21xR()+ 1 Figure 3. Distribution of the gluon polarisation ᭝G(x)/G(x) at Q2 = 3(GeV/c)2 d ᭝ ᭝ where F 2 is the spin-independent deu- for the two QCD fits with G > 0 and G < 0 performed by the COMPASS teron structure function and R is the Collaboration. The data points show the measured values from SMC [17], ratio of longitudinal and transverse HERMES [15, 16], and COMPASS (Table 1).

Vol. 18, No. 4, 2008, Nuclear Physics News 29 facilities and methods

᭝ ᭝ between Tu and Td. A few analyses aiming at the extraction of the transversity distributions have already been performed, and all the observed phenomena can be described in a unified scheme. In Figure 4 the results of our measured deuteron asymmetries are compared with the results of the most recent global analysis of Anselmino et al. [21] which uses the Collins asymmetries from HERMES (proton) and from COMPASS (deuteron), and the e+ e− → hadrons data from BELLE to fit the valence u- and ᭝ ᭝ d-quark distributions Tuv, Tdv, and ᭝0 h the Collins functions T Dq for favored and unfavored fragmentation (9-parameter fit). In Figure 5 the Figure 4. COMPASS results for p± Collins asymmetries [18] on deuteron from the 2003 and 2004 runs compared with the fit results of the global analysis of Anselmino et al. [21].

result from the SMC Collaboration for a few years by the HERMES Col- [17]. The picture that emerges clearly laboration, measuring semi-inclusive favors small values of ᭝G, a conclu- DIS events on a transversely polarized sion supported also by the recent mea- proton target, providing evidence that surements at RHIC. both the transversity PDF and the Col- lins FF are different from zero. Inde- pendent evidence that the Collins COMPASS Results on mechanism is a real measurable effect Transverse Spin has come from the recent analysis of The COMPASS experiment has the BELLE Collaboration. Our mea- measured for the first time single had- surements on the deuteron do not ron transverse spin asymmetries in DIS show any appreciable effect, and all of high energy muons on deuterons and the measured asymmetries are com- protons, scattering the 160GeV/c patible with zero, as apparent from muon beam on transversely polarized Figure 4, which shows our latest 6 ± LiD and NH3 targets. Also in this results for p [18] from the 2003 and case, several asymmetries have been 2004 runs (the Collins and Sivers Figure 5. The transversity distributions ᭝ investigated, in particular for a two asymmetries on the deuteron for non- Tqv for the u- and d-quarks hadron system, exclusive r, and l identified hadrons from the 2002, extracted with a global analysis of all hyperons, but in this short report I will 2003, and 2004 data have already the existing data by M. Anselmino mention only the results for Collins been published [19, 20]). et al. (lower red curves). The dotted and Sivers effects. The deuteron being isoscalar, the curves are the corresponding helicity Collins asymmetries definitely dif- null result from COMPASS can be distributions and the blue curves ferent from zero have been reported understood in terms of cancellation indicate the so-called Soffer bound.

30 Nuclear Physics News, Vol. 18, No. 4, 2008 facilities and methods

extracted transversity distributions is only marginally compatible with necessity of full QCD analysis ᭝ Tqv for the u- and d-quarks are plot- the finding of HERMES, and has to have been clearly established. ted and compared to the correspond- be understood. b. The comparison with the static ing helicity distributions. This is the quark model was misleading. Even first time the transversity distributions starting with three valence quarks in are extracted with a global analysis of Is the Nucleon Spin Puzzle Solved? an S-state, the Melosh rotation, all the existing data, but it is already Twenty years after the EMC mea- which gives the connection between possible to note that the transversity surement, it is fair to say that thanks to the spin states in the rest frame and distributions (in particular the d-PDF) a huge theoretical and experimental in the infinite momentum frame, are considerably smaller than the cor- effort many things have been under- introduces a nontrivial spin structure responding helicity distributions, and stood: and correlations between quark spin do not saturate the so-called Soffer and quark angular momentum; bound. Most rewarding is the com- a. The original measurement sug- c. The possibility that most of the parison of our very recent prelimi- gested that ᭝Σ might have been missing spin be carried by the nary results of the Collins asymmetry as small as zero. After a new gluon seems ruled out by the of the proton [22] with the expecta- generation of experiments we present direct measurements of tions from the same global analysis. know that it is not so; ᭝Σ is mea- ᭝G. The precision on ᭝G will The comparison between our new sured to be 0.3 with good preci- improve in the next years thanks to data and the predictions of Ansemino sion. Accurate comparisons with the combined analysis of the DIS et al. is shown in Figure 6. The agree- the predictions of sum-rules (in data and of the polarized proton- ment is very good, and a clear sign of particular with the fundamental proton data coming from RHIC, the soundness of the physics which is Bjorken sum-rule) have been but without a dedicated e-p col- behind it. possible. The interconnection lider it seems difficult to assess We have also measured the Siv- between ᭝Σ and ᭝G and the with high accuracy which fraction ers asymmetry. All the asymmetries we have measured on the deuteron target are small, if any, and compatible with zero. On the other hand, the HERMES p+ data on a proton target have also provided convincing evidence that the Sivers mechanism is ᭝T at work, and that 0 uv is different from zero. The approximately zero Sivers asymmetries for positive and negative hadrons observed in COM- ᭝T ∼−᭝T PASS require 0 uv odv, a relation that is also obtained in some models, and which anyhow has a simple physical interpretation if the Sivers distortion of the PDF of the nucleon is associated with the orbital angular momentum of the u- and d-quarks. The preliminary results from our proton data [22] suggest Sivers asymmetries that are compatible with zero both for nega- Figure 6. COMPASS preliminary results of the Collins asymmetry of the proton tive hadrons and for positive had- from 2007 data [22]. The curves are the expectations from the global analysis rons. The result for positive hadron of Ansemino et al. [21].

Vol. 18, No. 4, 2008, Nuclear Physics News 31 facilities and methods

of the nucleon spin is due to the 3. COMPASS Collaboration, P. Abbon 15. HERMES Collaboration, A. Airapetian gluon and which is due to the et al., Nucl. Instrum. Meth. A 577 etal., Phys. Rev. Lett. 84 (2000), 2584. orbital momentum. (2007), 455. 16. D. Hasch, HERMES Collaboration., d. New possibilities to understand the 4. EMC Collaboration, J. Ashman et al., AIP Conf. Proc. 915 (2007), 307. Phys. Lett. B206 (1988), 364; Nucl. 17. SMC Collaboration, B. Adeva et al., spin structure are offered by the Phys. B328 (1989), 1. Phys. Rev. D70 (2004), 012002. investigation of transverse spin 5. R. L. Jaffe and X. Ji, Phys. Rev. Lett. 18. COMPASS Collaboration, M. Alek- effects. New properties of matter 67 (1991), 552. seev et al., CERN-PH-EP/2008-002, have been unveiled. The Collins 6. J. Collins, Nucl. Phys. B396 (1993), 161. arXiv:0802.2160 hep-ex.. effect is there and precise measure- 7. D. Sivers, Phys. Rev. D41 (1990), 83. 19. COMPASS Collaboration, V. Y. ments of transversity and of the 8. B. L. G. Bakker, E. Leader, and T. L. Alexakhin et al., Phys. Rev. Lett. 94 quark orbital angular momentum Trueman, Phys. Rev. D70 (2004), (2005), 202002. 20. COMPASS Collaboration, E. S. Ageev are at hand. 114001. 9. COMPASS Collaboration, E. S. Ageev et al., Nucl. Phys. B765 (2007), 31. et al., Phys. Lett. B633 (2006), 25. 21. M. Anselmino et al., Phys. Rev. D75 As it has always been since the dis- 10. COMPASS Collaboration, V. Y. Alex- (2007), 054032 and PKU-RBRC covery of Stern and Gehrlach in 1921, akhin et al., Phys. Lett. B647 (2007), 8. Workshop on Transverse Spin Physics, the history of spin is a history full of 11. SMC Collaboration, B. Adeva et al., Peking, June 30–July 4, 2008. surprises. Phys. Rev. D58 (1998), 112001. 22. S. Levorato, COMPASS Collaboration, 12. HERMES Collaboration, A. Airapetian Transversity 2008, Ferrara, Italy, May etal., Phys. Rev. D71 (2005), 012003. 28–31, 2008, arXiv:0808.0086 hep-ex. References 13. E143 Collaboration, K. Abe et al., 1. S. D. Bass, Rev. Modern Phys., 77 (2005), Phys. Rev. D58 (1998), 112003. FRANCO BRADAMANTE 1257. 14. E155 Collaboration, P. L. Anthony University of Trieste and Trieste 2. V. Barone et al., Phys. Rep. 359 (202), 1. et al., Phys. Lett. B463 (1999), 339. Section of INFN, Italy

32 Nuclear Physics News, Vol. 18, No. 4, 2008 impact and applications

Industrial PET at Birmingham

In the 75 years since the first requiring measurement of millions of like a fluid. The figure shows (a) the observation of the positron in cosmic- individual g-ray pairs to reconstruct an track of the particle over a period of a ray showers, positron emission accurate 3D image, which makes it few seconds, (b) the “occupancy” dis- tomography (PET) has developed into unsuited to observing the dynamics of tribution representing the fraction of one of the most powerful diagnostic fast flows. For many applications, the the run time during which the particle tools in medicine. For clinical studies, alternative technique of positron emis- was found in each region, averaged a fluid of interest is labeled with a sion particle tracking (PEPT), devel- over a period of many minutes, and (c) positron-emitting radioisotope and oped at Birmingham, proves more its average velocity at each position. introduced into the body. By detecting useful. In PEPT, a single, radioac- Assuming that the tracer’s behavior is the pairs of back-to-back 511 keV tively labeled tracer particle is tracked representative of all the particles in the g-rays produced in positron-electron as it moves around inside the system bed, the time-averaged quantities (b) annihilation, a PET scanner builds up under study. The particle’s instanta- and (c) should describe the average a quantitative 3D map of the concen- neous location is determined by trian- number density of particles in the bed tration of this fluid, revealing its gulation using a small number of and their average velocity field. As uptake by individual organs. For detected pairs of back-to-back g-rays well as studying granular material, example, a labeled form of glucose is (Figure 1). In principle just two PEPT can also be used to study the used to map metabolic rate and iden- detected pairs provide an estimate of behavior of viscous fluids, by intro- tify tumors (which metabolize glucose location, since each defines a line ducing a small neutrally buoyant parti- rapidly). passing close to the tracer position. In cle as a flow follower. Routinely at A similar approach can be used to practice more are required to obtain an Birmingham, the tracer is located 500 study flow inside engineering sys- accurate location, especially as many times per second (so that a particle tems. The 511 keV g-rays are highly of the detected pairs are corrupt, for moving at 5 m/s is observed at inter- penetrating (50% are transmitted example because one or both of the g- vals of 10 mm along its path) to a pre- through 11-mm steel) so non-invasive rays has scattered prior to detection. cision of around 1 mm. measurements can be made on real Given a large enough sample, the This work dates back to the early industrial equipment. The potential of cluster of useful lines that converge on 1980s when Mike Hawkesworth at PET for such studies has been the tracer position can be distin- Birmingham was asked by colleagues explored and developed at the Univer- guished from the broad background of from Rolls Royce if he could find a sity of Birmingham for over 20 years. lines due to corrupt pairs. An iterative way of imaging the lubricant distribu- Unfortunately PET is a slow technique, algorithm is used, which starts with a tion inside an operating aero-engine. sample of typically 100 pairs, calcu- Hawkesworth realized that PET, lates their centroid, then discards the which was then just starting to be used outliers and recalculates using just the in medicine, could in principle pro- remaining pairs. This process contin- vide the answer. Simultaneously, ues until all corrupt pairs have been Eddie Bateman and his team at the discarded. Rutherford Appleton Laboratory had Figure 2 shows an example of been developing a “positron camera” PEPT data, following the motion of a based on a pair of gas-filled multiwire single particle within a fluidized bed. proportional chambers (MWPCs), Such systems are widely used in which they hoped would provide an industry for processing granular mate- inexpensive detection system for med- rial: if gas (often air) is blown upward ical PET. Instead, this system was Figure 1. Basis of PEPT: tracer through a bed of particles with suffi- developed into a robust camera for particle is located using a small cient velocity the particles become performing engineering PET. The number of back-to-back g-ray pairs. suspended and the bed moves around camera became operational in 1984,

Vol. 18, No. 4, 2008, Nuclear Physics News 33 impact and applications

few years the world of medical PET has been revolutionized by the introduction of combined PET/CT scanners, in which a near-simultaneous X- ray image of a patient’s anatomy can be measured and superimposed on the functional PET image. As a result, a number of older PET centers decided to replace their existing PET scanners with PET/CT systems, and Birming- ham was able to acquire their old scanners. Like this, we have recently obtained four complete PET scanners Figure 2. Example of PEPT data, from a spouted fluidized bed: (a) short section as well as components from two oth- of particle track, (b) occupancy and (c) velocity field. ers, and have reconfigured them for our use. The detectors inside these scanners and shortly afterward was successfully developed a variety of off-the-shelf are grouped in modules, each with its used to measure PET images of radio- PET detector systems, including own electronics. A typical scanner actively labeled lubricant inside a gamma camera PET systems that were contains 32 such modules. A flexible small jet engine operating at full marketed as multipurpose imaging PEPT system can be constructed sim- power on a testbed. systems for nuclear medicine. In 1999 ply by arranging the modules in a dif- The link with Rolls Royce ended we replaced the MWPC camera with ferent geometry. Whereas for PET it is around 1990, but the Birmingham one of these systems, comprising a important to sample g-rays uniformly group continued to explore the use of pair of gamma camera heads operating around a complete circle, for PEPT PET in engineering. An early applica- in coincidence. Each head consists of tion was to study motion in fludized a sheet of sodium iodide scintillator beds, and PEPT was first developed as backed by an array of 55 photomulti- a way of observing the motion of large plier tubes (PMTs) that detect the particles within such a bed. In the sub- flash of light produced by a g-ray sequent 15 years the technique has interacting in the scintillator and local- been refined, and techniques have ize this to within a few mm. This sys- been developed for labelling a range tem is ideal for PEPT, with an open of tracer particles with sizes down to geometry able to accommodate large 100 mm. PEPT has been used by a rigs (Figure 3). It can record up to large number of university groups and 100 k g-ray pairs per second, com- by researchers from industries includ- pared to a maximum of 5 k per second ing petrochemicals, pharmaceuticals, from the MWPC system. food, and minerals processing, to Dedicated medical PET scanners study processes involved in the manu- generally use a different approach, facture of products ranging from phar- comprising hundreds of small, high- maceutical tablets to canned food and efficiency detectors, mounted in rings from washing powder to ice cream. about the patient. Such scanners offer The original MWPC positron cam- significantly higher sensitivity and era performed reliably for over 15 count rate than a gamma-camera PET years. During this period, the use of system, but the restricted field of view Figure 3. The gamma-camera system PET in medicine became more wide- is unsuitable for studying large engi- being used in a PEPT study of spread, and equipment manufacturers neering rigs. Fortuitously, in the last a fluidized bed.

34 Nuclear Physics News, Vol. 18, No. 4, 2008 impact and applications

any arrangement of detectors can be used provided the tracer is always in line between at least one pair. The resulting “modular positron camera” has the advantage that it is transport- able, so that PEPT studies can be performed outside the lab. In the last two years, this system has been used for several applications, including observing single particle motion inside a large fluidised bed at BP’s Hull site (230 km from Birmingham) and studying the casting of liquid aluminium into molds in the University Foundry (Figure 4). When the detector modules are packed closely together this system can detect up to 4 M g-ray pairs per second, allowing very accurate tracking of fast-moving tracers. Not all the work at Birmingham uses PEPT. Conventional PET has recently been used to study the blending Figure 4. The modular positron camera being used in a PEPT study of liquid of powders for pharmaceutical formu- aluminium casting. The detector modules are mounted inside protective boxes lation. Because each PET scan takes and arranged in four orthogonal stacks. several minutes, this study was carried out in stop/start mode: a small amount of labeled powder was added to the the Radial Ridge Cyclotron, which with maximum energies of 40 MeV mix and imaged, the blender was run commenced operating in 1960, but by (protons or alphas), 20 MeV (deuter- for a few seconds and then stopped for the late 1990s this cyclotron was ons), and 53 MeV (3He). It has proved another image, and so on. PET is espe- becoming increasingly unreliable, and extremely reliable, and in addition to cially suited for observing very slow the opportunity was taken to replace it producing the tracers required by the flows, and over the years we have per- with a more modern cyclotron. The Positron Imaging Centre it is used for formed a number of studies on flow of present Scanditronix MC40 Cyclo- a variety of research purposes, includ- liquid or gas through geological sam- tron was purchased second-hand from ing surface activation of components ples. Using components from one of the VA Medical Center, Minneapolis, for wear testing, and measuring radia- the medical scanners, we have also at the beginning of 2002, was moved tion effects on electronics destined for built what we believe to be the world’s to Birmingham and recommissioned use in space. The MC40 cyclotron largest PET scanner: a ring of 128 during 2002–2004, and has been fully also produces 81Rb daily for sale to detector blocks with an inner diameter operational since March 2004. hospitals across the United Kingdom. of 2.3 m. During 2005, we extended the layout The activity required in a PEPT Positron emitting isotopes are gen- by acquiring the switching magnet tracer depends on the tracer speed, the erally produced using a cyclotron. from the former Vivitron accelera- size of the system (detector separa- Birmingham has a long history of tor, which allows the beam to be tion), and the extent of g-ray attenua- developing and operating cyclotrons, switched between 12 independent tion in surrounding material. In a beginning with the Nuffield Cyclo- target stations. compact low-mass system accurate tron, which operated from 1948 until The MC40 is a flexible research high speed tracking can be achieved 1999. The PET work was started with cyclotron, delivering variable energy using a tracer with an activity of the aid of radioisotopes produced by beams of hydrogen and helium ions around 10 MBq, but for a large dense

Vol. 18, No. 4, 2008, Nuclear Physics News 35 impact and applications

system (e.g., a stirred water tank) techniques has been developed for Acknowledgments activities up to 40 MBq are optimal. labeling particles including poly- I thank all the colleagues who have Just as in medical PET, most stud- mers, plant seeds, catalysts, minerals, worked with me on these projects over ies at Birmingham use the radioiso- coal, metals, and microcrystalline the years, in particular Xianfeng Fan, tope 18F, which has a half-life of 110 cellulose down to 100 mm in size. Andy Ingram, and Jonathan Seville, minutes, but whereas medical PET Tracer particles produced in this way and I acknowledge with gratitude the centers generally produce 18F by survive well in dry conditions or in continuing financial support from proton irradiation of water, which is organic solvents, but in an aqueous EPSRC. isotopically enriched in 18O, at environment the activity tends to Birmingham the alternative produc- leach away rapidly. A crude solution tion route using 3He on natural oxy- to this problem is obtained by paint- gen is used. In this way, everyday ing the surface of the tracer after materials such as glass or alumina labeling, thus sealing the activity beads can be directly activated for inside. A better approach is to use a use as PEPT tracer particles. Targets cationic radionuclide such as 61Cu containing oxygen are irradiated with (half-life 3.4 hours) or 66Ga (9.3 a 36 MeV 3He beam, producing 18F hours), which binds more irreversibly through the reactions 16O(3He, p)18F to particle surfaces. and 16O(3He, n)18Ne ⇒18F. In many Looking ahead, we consider that cases, the target is water (natural PET and PEPT may be of value in 18 water, not H2 O) so that the result is numerous untried fields. It’s surpris- DAVID PARKER a very dilute solution of radioactive ing what can be achieved using sec- Positron Imaging Centre, fluoride, which must then be attached ond-hand equipment (cyclotron and School of Physics and Astronomy to the particle of interest. A range of PET scanners)! University of Birmingham

36 Nuclear Physics News, Vol. 18, No. 4, 2008 meeting reports

The 13th International Conference on Capture Gamma-Ray Spectroscopy and Related Topics—CGS13

The 13th International Conference synergy of recent experiments in vari- The conference in Köln was a very on Capture Gamma-Ray Spectroscopy ous fields of nuclear physics with lively example of presentations, dis- and Related Topics, called CGS13 for recent advances in state-of-the-art cussions covering the overlapping short, was held from Monday, August shell-model methods, nuclear mean- regions between various exciting 25 to Friday, August 29 at the Institute field and beyond approaches also domains in the physics of atomic of Nuclear Physics of the Universität invoking the importance of symme- nuclei, and their study through the use zu Köln, with Prof. J. Jolie as the try concepts as a guiding principle to of a large set of complementary chairman. This conference, of rather understand the atomic nucleus. probes. Due to the large number of wide scope, already has a longstand- Nuclear Reactions including the participants (164 registered physicists ing tradition, going to 1969, when study of statistical properties of representing 28 different countries) the first edition was organized at nuclei formed a recurring theme in and the many high-quality abstracts Studsvik, Sweden, starting in Petten the present edition of CGS13. Tradi- submitted, on Tuesday, Wednesday, (the Netherlands) in 1974, Brookhaven tionally, Nuclear Astrophysics takes and Thursday morning, parallel ses- (USA) in 1978, Grenoble (France) in a particularly strong position in the sions had to be organized next to the 1981, coming into a 3-year cycle series of meetings and this was 16 plenary sessions. With the two lec- since then. The places the meeting again so in Köln, strongly emphasiz- ture rooms very close to each other, was held onward were Knoxville ing recent experimental work and the movement from one to the other (USA) in 1984, Leuven (Belgium) in pointing toward the need of the best went rather smoothly. 1987, Asilomar (USA) in 1990, possible input from theorists and Among the participants, there was Fribourg (Switzerland) in 1993, new theoretical developments. Time a very large fraction of young gradu- Budapest (Hungary) in 1996, Santa has also been devoted to have a cou- ate, postdoc, and junior staff people Fe (USA) in 1999, Prague (Czech ple of sessions on Nuclear Data. The present. At the same time, it is good Republic) in 2002, and Notre-Dame conference always has been the to mention that Till von Egidy of the (USA) in 2005. The tradition of place where much attention and Technische Universität Münich was alternating on both sides of the interest is given to new experimental the one physicist present who Atlantic Ocean, with a 3-year inter- techniques and facilities, covering a attended all 13 editions of the CGS val, will continue also this time. At whole range from new detector sys- conference. the special lunch meeting of the tems, development of new radioac- The program was densely packed Advisory and Program Board, an tive beams, over the use of neutrons and thus the conference trip on unanimous decision was made to (cold neutron beams, neutron Wednesday afternoon was very much have the next meeting in the series, sources). Also, sessions on practical welcome. The trip went first by bus to that is, CGS14, at the University of applications (covering material sci- the beautiful city of Linz, south of Guelph, moving to Canada for the ence, imaging, interface with other Köln, where a guided tour passed first time. The organization will be scientific disciplines such as chem- through the narrow alleys of this taken up by Prof. P. Garrett and a istry, biology, . .) were included at medieval little town. The way back local organizing team. the CGS13 conference. A particu- went relaxingly and with fine weather The series of CGS conferences is larly attractive part comes from the by boat on the river Rhine, passing characterized by a broad range of fact that neutrons can play a very through the beautiful region near Bad topics encompassing Nuclear Struc- important and fundamental role in Honnef and Köningswinter (close to ture, covering most recent develop- the study of basic physics. The ses- the “Siebengebirge“). The early night ments in both experimental and sion on Fundamental Physics took was coming with the boat arriving theoretical research. Many talks up that line of research and exciting near to the illuminated Dom in the showed the presence of a strong new results were presented. heart of Köln.

Vol. 18, No. 4, 2008, Nuclear Physics News 37 meeting reports

A poster session was organized (Univ.Ghent)—ended up splitting fine wines from the Baden region in the late afternoon on Tuesday. the prize among two very fine con- (Kaiserstuhl). This poster session sought the very tributions. One half went to a start- The local organizing team is to be best poster(s) presented by graduate ing graduate student from the congratulated for the impeccable orga- students and postdoctoral fellows University of Köln, Linus Better- nization of this 13th edition of the con- with an award of 500 Euro. The best mann, with a poster on mixed- ference: not only was a scientific poster for the ”the Founder’s symmetry states. The other half was program of very high quality arranged, Award,” an award that was inaugu- given to Steven Pain, a postdoctoral but the flow throughout the five-day rated in honor of the memories of fellow working at Oak-Ridge conference ran smoothly indeed in the the late Jean Kern, Subramanian National Laboratory (ORNL), with spacious Physics building, with ample Raman, and Gabor Molnar, all of a contribution on the development room for computing, having discus- whom played a major role in estab- of the ORRUBA Silicon Detector sions, and taking time at coffee breaks lishing thrust and growth of the Array. with cake and cookies. CGS13 will early meetings into a major interna- A memorable event was the con- definitely go into history as a worthy tional conference, had to be selected ference dinner, on Thursday evening, partner of this gallery of conferences. among a large number of high- held at the “Imhoff Schokoladenmu- quality contributions. The selection seum.” This event gave rise to the pos- KRIS HEYDE committee— H.Börner (ILL Greno- sibility of socializing in a relaxed Department of Subatomic ble), F. Käppeler (Forschungszen- atmosphere among the many partici- and Radiation Physics trum Karlsruhe), and K. Heyde pants, and this over a great buffet and University of Ghent(Belgium)

Hadron Physics Summer School 2008

More than 80 graduate and The HPSS2008 was jointly orga- the Universities Bonn, Bochum, and advanced undergraduate students from nized by scientists working at the Giessen. In addition, the HPSS2008 was 14 countries and 4 continents partici- Nuclear Physics Institute (http://www. sponsored by DAAD (German Aca- pated in the Hadron Physics Summer fz-juelich.de/ikp) of the Jülich Center demic Exchange Service) and DPG School HPSS2008 held at Physikzen- for Hadron Physics at Jülich Forschung- (Deutsche Physikalische Gesellschaft), trum Bad Honnef, Germany, August szentrum and by the DFG Transregio making the participation of young 11–15, 2008 (Figure 1). Similar to the TR 16 (Subnuclear Structure of Matter, motivated students into this challenging preceding COSY Summer School http://sfb-tr16. physik.uni-bonn.de/) of enterprise possible. (CSS) 2002, 2004, and 2006, this school consisted of lectures and working groups on theoretical, experimental, and accelerator aspects. The focus was on current issues in hadron physics with emphasis on the latest programs at the accelerators COSY (Jülich) and ELSA (Bonn), also fea- turing future FAIR projects like HESR/PANDA and PAX. During the very successful school, the students were given a guided tour to the Cooler Synchrotron COSY at Jülich Fors- chungszentrum. Figure 1. Participants of HPSS2008 in front of Physikzentrum Bad Honnef.

38 Nuclear Physics News, Vol. 18, No. 4, 2008 meeting reports

It is intended to conduct the HPSS contained and will also be an excellent For more detailed information, every second year. The series will be opportunity for graduate students and see:\\http://www.fz-juelich.de/ikp/ supplemented by lecture weeks in the early post-graduates to deepen the hpss2008/. alternate years, which will consist of knowledge gained at HPSS. invited lectures and student contribu- FRANK GOLDENBAUM tions. The lecture weeks are self- FZ Jülich

Vol. 18, No. 4, 2008, Nuclear Physics News 39 news and views

BEPC-II/BES-III Complex

On late Saturday afternoon July c-quarks, which have a mass that is The two bunches, which have a verti- 19, researchers at the Chinese Acad- about 3,000 times that of the electron, cal profile of only about five mil- emy of Science’s Institute of High are produced together with their lionths of a meter, are made to cross Energy Physics in Beijing produced equal-mass antimatter counterpart, each other in the center of the BES-III for the first time collisions in the anti-charmed quarks (c-quarks), in detector. Occasionally, an electron in upgraded BEPC-II electron positron head-on collisions of high energy one bunch hits a positron in the other collider that were observed in its electrons and anti-electrons (famil- bunch head-on and the two particles brand new associated detector, called iarly known as positrons). In these annihilate each other to produce a pair BES-III. Although BEPC-II and BES-III collisions, the electron and positron of particles: one containing a c-quark had already been carefully tested sepa- annihilate each other and in the pro- and an associated one that contains a rately, this was the first time they cess their energy is converted into the c-quark. These so-called charmed par- operated together. These first colli- massive c- and c-quark pair in accor- ticles rapidly decay into more conven- sions represent a major milestone of dance with Einstein’s famous relation tional particles like p- and K-mesons this project, which involved eight E = mc2. whose energies and velocities are pre- years of planning and construction. To accomplish this, the BEPC-II cisely measured in the BES-III spec- When it is fully operational, the team confines a tightly bunched clus- trometer. From these measurements, BEPC-II/BES-III complex will be the ter of approximately 50 billion elec- the properties of the parent charmed world’s premier facility for studying trons inside a vacuum tube that particles can be deduced. the properties of particles that contain threads through a ring of powerful BEPC-II is a major upgrade of a charmed quark (c-quark), the fourth electro-magnets that maintains the IHEP’s previous collider BEPC. The of an assortment of six different electron bunch in a nearly circular major change has been the addition of quarks that physicists have identified orbit. Likewise a similar “bunch” of a second ring of magnets that allows as the most fundamental building positrons is made to counter-rotate in the electron and positron beams to be blocks of matter. In BEPC-II, an identical second ring of magnets. stored separately. In BEPC, the electrons and positrons shared the same vacuum tube in a single ring of magnets, and this arrangement could accommodate only a single bunch each of electrons and positrons, thereby limiting the rate at which interesting particles are produced. The two separate rings of BEPC-II will allow for 93 bunches in each ring. In addition, BEPC-II has many other improvements including a more powerful injection accelerator that produces the high energy electrons and positrons, and an extensive use of superconducting technology, both for the acceleration and magnetic focusing of the stored electron and positron beams. The net effect of all of these improvements will be a more than hundred-fold increase in the collision Figure 1. The BESIII detector in the interaction region of BEPCII. rate.

40 Nuclear Physics News, Vol. 18, No. 4, 2008 news and views

approximately every ten minutes. A display of one of the first such events is shown in Figure 2. The collision rate in the initial test run was about a factor of 4,000 times slower that the project’s ultimate design goal of 6 or 7 charmed-particle pairs per second. This lower rate was partly because the researchers purposely limited the intensity of the electron and positron beams in order to avoid possible dam- age to the very sensitive detection sen- sors of the BES-III spectrometer while they made sure that everything is working as expected. The next day, intensities were increased and a ten- times higher collision rate was measured. Over the next several weeks the intensity of the beams will gradually be further increased while at the same time BES-III’s nearly 20,000 detec- Figure 2. The first charmed-meson pair event seen in BES-III. tion elements will be carefully adjusted and calibrated. When this process is completed, sometime in the early Fall, the BES-III research pro- The BES-III detector is completely crystal array enables the BES-III gram will begin. new with a number of major improve- detector to measure the energies and Recently, researchers working at ments over its predecessor, BES-II. velocities of the produced particles IHEP and at laboratories in Japan and These include its huge superconduct- with more than ten times better preci- the United States have observed a ing magnet, which produces a mag- sion than was previously possible with number of interesting and unexpected netic field throughout the detector that BES-II. To handle the huge data rates properties of charmed particles that is about 20,000 times stronger than the expected in the BES-III detector, a will be investigated with unique sensi- Earth’s magnetic field. This strong specialized state-of-the-art high-speed tivity with BES-III; these observations magnetic field deflects charged parti- data communication system has been have added substantially to the world- cles as they traverse the detector and developed and implemented. wide particle physics community’s by measuring the amount of deflection BEPC-II’s double ring system was interest in the BES-III research pro- researchers can make precision mea- completed in October 2006, beams gram. These new developments surements of the particles’ velocities. were first stored during the following include the surprising observation that This magnet, which is the most pow- month and first collisions were pro- neutral charmed mesons, that is, erful magnet in China, was built at duced in March 2007. The assembly mesons containing a c-quark and an IHEP by the laboratory’s research of the BES-III detector was completed anti-up quark (u-quark), spontane- staff. In addition, BES-III contains a in January of this year, and it was ously transform into anti-charmed large array of 6,240 crystals of moved into the interaction region in mesons (i.e., u- and c-quark mesons) Cesium Iodide that are used to mea- early April (see Figure 1). and vice versa, a phenomenon that sure the energies of the high-energy In last weekend’s initial test run, a was quite unexpected. BES-III will be gamma rays that are produced in the pair of charmed particles, where one uniquely able to perform important collisions. The combination of the contains a c-quark and the other a measurements that categorize this pro- superconducting magnet and the large c-quark, was recorded in the detector cess to help theoretical physicists

Vol. 18, No. 4, 2008, Nuclear Physics News 41 news and views

understand the root cause for these ciated particles in nature. In addition, by BES-III correspond to an approxi- transformations. Recently, there have the BES-II experiment at IHEP and a mately ten-year-long program of

been hints that inside so-called Ds number of experiments at other labo- intensive research. This research will mesons, which are particles comprised ratories have uncovered a new class of be carried out by an international team of a c-quark and an anti-strange quark particles that do not fit into the con- of researchers from China, Hong (s-quark), the constituent c- and ventional quark model scheme. To Kong, Germany, Japan, Russia, and s-quarks annihilate each other at a rate date, in spite of considerable effort, the United States. The observation of that seems to be higher than that pre- theorists have been unable to achieve first collisions in the BEPC-II/BES-III dicted by theory. If this discrepancy a compelling picture that describes facility was an important milestone in could be unequivocally established, these states. More detailed measure- this research program. which is something that BES-III is ments are necessary, and this is some- particularly well suited to do, this thing that BES-III will do. ULRICH WIEDNER would be striking evidence for a It is estimated that these and the Bochum whole new regime of forces and asso- many other topics to be investigated

Path for Mass Mapping of Superheavies is Open

It happened that just on August 8, to nuclear decay spectroscopy investi- Penning traps are nowadays power- 2008 (on the distinguished day of gations that are feasible in this region. ful tools for mass measurements of 08.08.08!) the SHIPTRAP collabora- As the isotopes of new elements exotic short-lived nuclides. The main tion at GSI succeeded in directly mea- have been identified by their a-decay, Penning trap techniques used at the suring the masses of three nobelium it was previously thought that about a SHIPTRAP-facility are very similar to isotopes. Never before have mass val- dozenlong a-chains, which originate those pioneered by ISOLTRAP at ues of any isotope of the trans-ura- from superheavy nuclides and end in ISOLDE/CERN. SHIPTRAP, however, nium, or even trans-fermium elements the region of well-known masses, can utilizes exotic radionuclides from of the Periodic Table been directly help to determine, although indi- heavy-ion fusion reactions after in- determined. Since the idea of the rectly, the mass values of superheav- flight separation at SHIP, which are existence of an island of superheavy ies. However, the attempts to stopped in a gas cell, then extracted, nuclides was put forward about forty complete this goal by searching for cooled, and bunched with subsequent years ago, heroic attempts have been some unknown a-emitters in the long undertaken to reach this alluring site chains were unsuccessful so far in the sea of nuclear instability. Step- because of very small a-decay proba- by-step discoveries of new superheavy bilities. Thus, direct mass measure- elements, performed over the last ments of superheavies became the decades at GSI (Darmstadt) and at only, but challenging, option left. JINR (Dubna), paved the way toward About ten years ago, H.-Jürgen this mysterious island. Being landed, Kluge came up with the idea to install we still do not know too much on its a Penning trap system behind the extension on the chart of the nuclides. velocity filter SHIP at GSI in order to The masses, that is, the total bind- enable this kind of direct measure- ing energies, allow us to explore the ment for rare isotopes produced in landscape of the predicted island and to fusion-evaporation reactions at SHIP, shed light on the structure and the sta- utilizing the intense primary beam bilizing shell effects of superheavies provided by the heavy-ion accelera- Figure 1. Time-of-flight cyclotron providing information complementary tor UNILAC. resonance for doubly charged 253No-ions.

42 Nuclear Physics News, Vol. 18, No. 4, 2008 news and views

this limit will be pushed further down: It is planned to install a cryogenic gas- stopping cell and to introduce a non- destructive detection technique where a mass value can be obtained using only one single ion for a mass determination. This activity is underway in collaboration with groups from GSI, Max- Planck Institute for Nuclear Physics in Heidelberg, from different universities such as University of Mainz, München, and Giessen, as well as from the St. Petersburg Nuclear Physics Institute.

Figure 2. Alpha-decay chains starting from darmstadtium isotopes and passing the directly mass-measured nobelium nuclides.

injection into a double Penning-trap value for this nuclide on a level of a system. After the isobar selection in the few times 10−8 accuracy. first trap, the mass of a charged particle The position of the measured nobe- is determined from its cyclotron lium isotopes in the a-decay chains is frequency, which is measured by a shown in Figure 2. As can be seen from time-of-flight ion-cyclotron resonance this figure the mass values up to 269Ds technique. With this method one can and 270Ds (Z=110) are linked via alpha- determine the mass value precisely. The chains and can now be connected to the MICHAEL BLOCK accuracy of Penning trap mass spec- directly determined nobelium mass val- GSI, Darmstadt trometers achievable for radioisotopes, ues. Notable information about the struc- which is typically about 10−8 (corre- ture of superheavies can be derived from sponding to 1keV in the region of masses of different nobelium isotopes, A≈100) is superior to all other meth- which have a neutron number around the ods. A great advantage of SHIPTRAP semi-magic N=152. Just this number of is its exceptional capability to measure neutrons luckily constitutes the nuclide directly the masses of trans-uranium 254No whose total binding energy was nuclides toward superheavies. measured directly at the SHIPTRAP. During the last experimental run As a consequence of this pioneering in August 2008 the masses of three experiment the door for a mass mapping nobelium isotopes (Z = 102) with in the region of superheavy elements is mass numbers A = 252, 253, and 254 open. At present, nuclides with produc- were measured at SHIPTRAP. A tion cross-sections on the level of 500 time-of-flight resonance curve for nbarn are accessible for direct mass 253 No is shown in Figure 1. It allows measurements with SHIPTRAP. With YURI NOVIKOV determining the so far unknown mass planned improvements of the system PNPI, St. Petersburg

Vol. 18, No. 4, 2008, Nuclear Physics News 43 news and views

IBA-Europhysics Prize 2009 for Applied Nuclear Science and Nuclear Methods in Medicine Call for Nominations

The Nuclear Physics Board of the /ific.uv.es/epsnpb/ and the website of 4. The Prize shall be awarded to one EPS calls for nominations of the 2009 EPS, www.eps.org (EPS Prizes, IBA- or more researchers. IBA-Europhysics prize. The award will Europhysics Prize). 5. The Prize shall be awarded without be made to one or several individuals for The deadline for the submission of restrictions of nationality, sex, race, outstanding contributions to Applied the proposals is January 15, 2009. or religion. Nuclear Science and Nuclear Methods Sponsored by Ion Beam Applica- 6. Only work that has been published and Nuclear Researches in Medicine. tions, Belgium. in refereed journals can be consid- The Board would welcome pro- ered in the proposals for candi- posals that represent the breadth and dates to the prize. General Description strength of Applied Nuclear Science 7. The NPB shall request nominations The European Physical Society and Nuclear Methods in Medicine in to the Prize from experts in Nuclear (EPS), through its Nuclear Physics Europe. Science and related fields who are Board (NPB), shall award a Prize to Nominations should be accompa- not members of the Board. Call for one or more researchers who have nied by a completed nomination form, nomination will be published in made outstanding contributions to a brief curriculum vitae of the nomi- Europhysics News, Nuclear Physics Applied Nuclear Science and Nuclear nee(s), and a list of major publications. News International, and at the Methods and Nuclear Researches in Letters of support from authorities in homepage of the IOP journal Medicine (investigation, aid to diag- the field that outline the importance of “Physics in Medicine and Biology.” nosis, and/or therapy). the work would also be helpful. 8. Self-nominations for the award Such contributions shall represent Nominations will be treated in shall not be accepted. the breadth and strength of Applied confidence and although they will be 9. Nominations shall be reviewed by Nuclear Science and Nuclear Methods acknowledged there will be no further a Prize Committee appointed by in Medicine in Europe. communication. Nominations should the NPB. The Committee shall be sent to: consider each of the eligible nomi- Selection Committee IBA Prize, Prize Rules nations and shall make recommen- Chairman Prof. G. Viesti, dations to the NPB, taking also Dipartimento di Fisica,, Galileo 1. The Prize shall be awarded every into account reports of referees Galilei,“ Università di Padova, two years. who are not members of the Board. Via Marzolo 8, I-35131 Padova, 2. The Prize shall consist of a 10.The final recommendation of the Italy. Phone/Fax: +32 049-8277124. Diploma of the EPS and a sum of NPB and a report shall be submit- E-mail: [email protected] or giuseppe. 5000 € (to be shared, in case of ted for ratification to the Executive [email protected] more than one laureate). Committee of the EPS. For nomination forms and more 3. The money of the prize is provided detailed information see: the website by the Belgian Company IBA (Ion GIUSEPPE VIESTI of the Nuclear Physics Division, http:/ Beam Applications). Padova, Italy

63 Nuclear Physics News, Vol. 18, No. 4, 2008 calendar

2009 March 30–April 1 June 15–17 January 12–16 Pisa, Italy. EURISOL Design Study Bad Honnef, Germany. Precision Stellenbosch, South Africa. Lasers and Town Meeting Experiments of Lowest Energies for Fun- Accelerators http://www.eurisol.org/site01/town_ damental Tasts and Constants http://academic.sun.ac.za/lasers& meeting-t-202.html http://www.mpi-nd.mpg.de/blaum/events/ accelerators/ heraeus09/ April 24–May 1 June 21–26 Erice, Sicily, Italy. Workshop on January 19–28 New London, NH, USA th Hadron Beam Therapy of Cancer Stellenbosch, South Africa. 20 Chris Gordon Conference on Nuclear Chemistry http://erice2009.na.infn.it/ Engelbrecht Summer School in Theoreti- (Nuclear Structure) cal Physics http://www.grc.org/programs.aspx? http://academic.sun.ac.za/summerschool/ May 4–8 year=2009&program=nuchem 2009.html Dubrovnik, Croatia, Nuclear Structure and Dynamics June 30–July 4 January 26–30 http://www.phy.hr/~dubrovnik09/ Dubna, Russia. Nuclear Structure and Bormio, Italy. XLVII International Related Topics Winter Meeting on Nuclear Physics May 4–8 http://theor.jinr.ru/~nsrt/2009/ http://panda.physik.uni-giessen.do:8080/ Vienna, Austria. International Topical September 27–October 3 indics/conferenceDisplay.py?confId=7 Meetingon Nuclear Research Applica- Milos, Greece tions and Utilization of Accelorators 8th European Research Conference on March 16–20 (AccApp’09) “Electromagnetic Interactions with Nucle- Bochum, Germany. European Nuclear http://www-pub.iaea.org/MTCD/Meetings/ ons and Nuclei” (EINN 2009) Physics Conference Announcements.asp?confId=173 http://www.iasa.gr/EINN_2009/ http://www.epl.rub.de/EUNPC May 13–16 September 28–October 2 March 21–24 Chateau de Cadarache, France Sochi, Russia International Sympo- Prague, Czech Republic. International International Workshop on Nuclear sium on Exotic Nuclei EXON 2009 Conference on Compating in High Energy Fission and Fission-Product Spectroscopy http://exon2009.jinr.ru/ and Nuclear Physics CHEP’ 09 hhttp://www.fission2009.com/ http://www.particle.cZ/conferences/ November 29–December 4 chep2009/ Napa, California, USA. 4th Asia- June 2–5 Pacific Symposium on Radiochemistry Mackinac Island, Michigan, USA March 29–April 4 (APSORC’09) 3rd International Conference on Knoxville, Tennesse, USA. Quark http://apsore2009.Berkeley.edu/ “Collective Motion in Nuclei under Matter 2009 Extreme Conditions” (COMEX 3) http://www.phy.ornl.gov/QM09 http://meetings.nscl.msu.edu/COMEX3/ 2010 July 19–23 Heidelberg, Germany. Nuclei in the Cosmos NIC XI http://www./sw.uni-heidelberg.de/nic2010

More information available under: http://www.nupecc.org/calendar.html . . . and check also http://www.ect.itÞMEETINGS

44 Nuclear Physics News, Vol. 18, No. 4, 2008