Nuclear Physics News International
Volume 27, Issue 3 July–September 2017
FEATURING: Nuclear Data • Deuteron Electric Dipole Moment • 0νββ Decay
10619127(2017)27(3)
Nuclear Physics News Volume 27/No. 3
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 Maria José Garcia Borge, Madrid (Chair) Eugenio Nappi, Bari Rick Casten, Yale Klaus Peters, Darmstadt Jens Dilling, Vancouver Hermann Rothard, Caen Ari Jokinen, Jyväskylä Hideyuki Sakai, Tokyo Yu-Gang Ma, Shanghai Calin Ur, Bucharest Richard Milner, MIT
Editorial Offi ce: 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 (from countries not covered by the Editorial Board and NuPECC) Argentina: O. Civitaresse, La Plata; Australia: A. W. Thomas, Adelaide; Brasil: M. Hussein, São Paulo; India: D. K. Avasthi, New Delhi; Israel: N. Auerbach, Tel Aviv; Mexico: E. Padilla-Rodal, Mexico DF; Russia: Yu. Novikov, St. Petersburg; Serbia: S. Jokic, Belgrade; South Africa: S. Mullins, Cape Town.
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Vol. 27, No. 3, 2017, Nuclear Physics News 1 Nuclear Physics Volume 27/No. 3 News
Contents Editorial The NuPECC Long Range Plan 2017: Perspectives in Nuclear Physics by Angela Bracco...... 3 Feature Articles A New Look to Nuclear Data by E. A. McCutchan, D. A. Brown, and A. A. Sonzogni...... 5 COSY Prepares the First Measurement of the Deuteron Electric Dipole Moment by Paolo Lenisa and Frank Rankmann...... 10 Searching for 0νββ Decay in 136Xe: Toward the Ton-Scale and Beyond by T. Brunner and L. Winslow...... 14 Facilities and Methods The Actual AMS Capabilities at the University of Cologne by Alfred Dewald...... 20 PANDA: Strong Interaction Studies with Antiprotons by Klaus Peters, Lars Schmitt, Tobias Stockmanns, and Johan Messchendorp...... 24 Twenty Years of VERA: Toward a Universal Facility for Accelerator Mass Spectrometry by Robin Golser and Walter Kutschera...... 29 Meeting Reports The 26th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2017 by Russell Betts, Olga Evdokimov, and Ulrich Heinz...... 35 Jefferson Lab Hosts Workshop on New Scientific Applications of its Low Energy Recirculator Facility by S. Benson and G. Krafft...... 37 News and Views ESF After ESF: The Launch of Science Connect by Jean-Claude Worms...... 38 An Important Milestone: Groundbreaking Ceremony for the FAIR Accelerator Facility by Ingo Peter...... 40 Calendar...... Inside back cover
Cover Illustration: The cover depicts a CAD drawing of the PANDA Detector in the foreground. The background shows the same drawing in kaleidoscopic reflections through a PANDA DIRC bar, which is made of highly polished fused silica – see article on page 24.
2 Nuclear Physics News, Vol. 27, No. 3, 2017 editorial
The NuPECC Long Range Plan 2017: Perspectives in Nuclear Physics
The process involved in the prepa- stadtium” in Darmstadt, from 11–13 ration of LRPs requires dedicated ef- January 2017. The Town Meeting was fort from many physicists of the nu- attended by almost 300 participants, clear physics community and from all including many young scientists. The NuPECC Members. programme contained, in addition Similar to several countries in the to the presentation of the Working world beyond the European boundar- Groups, sessions on future facilities: ies, today Nuclear Physics is defi ned FAIR, the ISOL facilities (SPIRAL2, as a fi eld including different research ISOLDE, and SPES), ELI-NP, NICA, domains sharing the diffi cult but stim- and the Dubna Superheavy Element ulating task to study nuclear matter Factory, as well as a presentation for in all its forms and of exploring their CERN from its scientifi c director. For possible applications. This knowledge the international context the over- NuPECC is essential if one wants to address views given by the Chairs of NSAC Long Range Plan 2017 several key issues for the understand- (USA) and ANPhA (Asia) were much Perspectives ing of the different stages concern- appreciated. The Town Meeting was in Nuclear Physics ing the origin and the evolution of concluded by a general discussion. the universe. The subfi elds of nuclear The recommendations with their physics defi ned by NuPECC span the wording were extensively discussed, areas of nuclear physics and its ap- not only at the town meeting but also 19 June 2017 was a special day plications: Hadron Physics, Proper- at the following NuPECC meetings. for NuPECC. Indeed, that day the ties of Strongly Interacting Matter It is not possible here, due to space “Long Range Plan for Nuclear Re- (at extreme temperatures and baryon limits, to quote them directly in their search in Europe” was released after number density), Nuclear Structure complete form and thus the reader is approximately 20 months of work for and Dynamics, Nuclear Astrophysics, invited to read our webpage (http:// its preparation. From the time it was Symmetries and Fundamental Interac- www.nupecc.org/pub/lrp2017.pdf). announced, at the end of 2015, the nu- tion, as well as Applications and Soci- In short, the recommendation sec- clear physics community was looking etal Benefi ts. tion includes the following: (1) a rec- forward to having it ready since this Two Conveners and three Liaison ommendation for the construction and document plays the role of an impor- Members of NuPECC were assigned operation of the fl agship facility FAIR tant reference and guide for the fi eld to each Working Group corresponding with its experimental programme at for at least the next six years. to one of the subfi elds given above. the four scientifi c pillars APPA, CBM, The delivery of long range plans The Working Groups were given the NUSTAR, and PANDA; (2) support (LRPs) represents the core of Nu- charge to delineate the most exciting for construction, augmentation, and PECC’s mission, which is “to provide physics in their subfi elds, to high- exploitation of world-leading ISOL advice and make recommendations light recent achievements and future facilities in Europe; (3) the exploita- on the development, organisation and perspectives. Draft reports from the tion of the existing and emerging fa- support of European nuclear research Working Groups were presented and cilities (the latter being ELI-NP and and of particular projects.” In the past discussed in internal workshops and at NICA); (4) support for ALICE and four LRPs were issued, in November NuPECC Meetings. the heavy-ion program at the LHC 1991, December 1997, April 2004 and A Town Meeting to discuss the with the planned experimental up- December 2010. NuPECC LRP was held at the “darm- grades; (5) support to the completion
The views expressed here do not represent the views and policies of NuPECC except where explicitly identifi ed.
Vol. 27, No. 3, 2017, Nuclear Physics News 3 editorial
of AGATA in full geometry; (6) Sup- worldwide, outside Europe (the larg- Acknowledgments port for Nuclear Theory. In addition, est fraction being in the United States In addition to the thanks to the the particular role of R&D for future and Japan), is underlined, resulting many scientists contributing to the projects and of education and training in major achievements in the fi eld. preparation of this long range plan, I are underlined in the recommendation These collaborations are expected to convey special thanks to Karin Füssel section. continue and to be reinforced in the (from GSI/FAIR, Darmstadt) for the In the introduction chapter one can future. organization of the town meeting and fi nd special mention to the contribu- Let me conclude by saying that this to Mara Tanase (from ELI-NP, Bucha- tion received by the European Com- editorial is not only intended to inform rest) for the technical editing and the mission to the different facilities, the on the release of the long range plan, layout of the volume. ones focusing on hadron physics and but it is also intended to thank all the the ones on nuclear structure and as- people involved directly or more indi- trophysics (presently in the ENSAR2 rectly in this process. Now these ac- integrated activity). Concerning the tive players in the fi eld are expected to more general scientifi c context, in further enhance the vitality of the fi eld which the Nuclear Physics infrastruc- by using this long range plan as a key tures are placed, the relation of Nu- tool for this purpose. Indeed, it will be PECC with ESFRI is very important very important in the coming years to and fruitful. implement the objectives outlined in Last but not least, in the introduc- the recommendations, in particular tion and also in various chapters, the also those that go beyond the capabili- ANGELA BRACCO role of international collaborations ties of an individual country. University of Milan; NuPECC Chair
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READ LEARN DISCUSS PARTICIPATE
4 Nuclear Physics News, Vol. 27, No. 3, 2017 feature article
A New Look to Nuclear Data E. A. McCutchan, D. A. Brown, and A. A. Sonzogni National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY, USA
Introduction tion codes and often the users are not even aware that they Databases of evaluated nuclear data form a cornerstone are using ENDF/B data libraries (such as various applica- on which we build academic nuclear structure physics, tion-tailored cross-section libraries). The most well-known reaction physics, astrophysics, and many applied nuclear applications include general particle transport codes used technologies. In basic research, nuclear data are essential in nuclear reactor, radiation shielding and health physics for selecting, designing, and conducting experiments, and applications (e.g., MCNP6, SCALE, GEANT4); isotope for the development and testing of theoretical models to burn-up codes used for the time-dependent nuclear reactor understand the fundamental properties of atomic nuclei. analyses, nuclear waste managements, and radiochemical Likewise, the applied fields of nuclear power, homeland applications (e.g., ORIGEN, CINDER); and other appli- security, stockpile stewardship, and nuclear medicine all cation code systems that use covariance data to estimate have deep roots requiring evaluated nuclear data. Each of nuclear data uncertainty in application metrics (e.g., TSU- these fields requires rapid and easy access to up-to-date, NAMI, WHISPER). comprehensive, and reliable databases. The Department The U.S. Nuclear Data Program supports two additional of Energy (DOE)–funded U.S. Nuclear Data Program is a databases that complement and underpin the primary da- specific and coordinated effort tasked to compile, evalu- tabases; the Nuclear Science References Database (NSR) ate, and disseminate nuclear structure and reaction data [3] and the Exchange FORmat Database (EXFOR) [4]. such that it can be used by the worldwide nuclear physics NSR contains bibliographic information on low- and in- community. termediate-energy nuclear physics articles including more than 220,000 publications and secondary references span- Overview of Our Databases ning the 100 years of nuclear physics research. The EX- Within the U.S. Nuclear Data Program (USNDP), data FOR library includes a complete compilation of experi- are filtered into two primary databases; the Evaluated mental neutron-induced reactions, selected compilations Nuclear Structure Data File (ENSDF) containing nuclear of charged-particle-induced and photon-induced reactions, structure and decay data, and the Evaluated Nuclear Data and assorted high-energy and heavy-ion reaction data. The File (ENDF/B) containing nuclear reaction data. EXFOR library is the most comprehensive collection of ENSDF [1] contains experimentally determined nuclear experimental nuclear reaction data available. The USNDP structure and decay data for all known nuclei. The results coordinates compilation of EXFOR data experiments per- derived following each specific nuclear reaction and de- formed in North America. cay mode are individually cataloged and then combined The newest addition to the supporting databases is in a critical analysis of all measurements to derive recom- XUNDL (eXperimental Unevaluated Nuclear Data List), mended properties for each quantum state and its decays. a database [5] containing critical compilations of current The uncertainties on each derived quantity are carefully journal articles on experimental nuclear structure and radio- evaluated. ENSDF is the only database in the world of this active decay data presented in the same format as ENSDF. kind and is updated on a monthly basis. The evaluated data It takes, on average, 7–8 years to revisit and re-evaluate all from ENSDF are used in a number of tools utilized by the 3,300 nuclei currently contained in ENSDF. XUNDL was nuclear physics community, including Monte Carlo codes developed to complement ENSDF and provide users with like MCNP and GEANT, medical dosimetry files, Ortec data from publications which have not yet been included and Canberra isotope identification software, Nuclear Wal- into ENSDF. Presently, over 15 experimental journals are let Cards, and more. scanned on a frequent basis and relevant articles incor- The ENDF/B library [2] contains nuclear reaction data porated into XUNDL within two months of publication. mainly for use in nuclear applications, including cross-sec- Supplemental material provided by authors and associated tions, outgoing particle distributions, fission product yields, with published papers can also be included. Such additions as well as atomic reaction data and decay data. Users of are highly encouraged, particularly in instances where the ENDF/B data frequently access the data through applica- publication has a length limitation.
Vol. 27, No. 3, 2017, Nuclear Physics News 5 feature article
Figure 1. Q value for beta-delayed neutron emission for the entire chart of nuclides as plotted using the Nu- Dat application.
and encourage community participation in improving the databases and corre- sponding software. In 2016, more than four million electronic retrievals were made from the NNDC website, access- ing various databases and online appli- cations. By far, the most popular prod- uct (at over 60% of the total retrievals) is the application NuDat. NuDat pro- vides users many options for displaying the nuclear structure and decay data in ENSDF, from the entire nuclear chart, to a single nucleus, and from tabular nu- Interacting with Structure Databases merical data to sophisticated plotting capabilities. Many All databases can be quickly and easily searched using nuclear properties can be visualized by selecting from op- Web applications available at the National Nuclear Data tions at the top of the chart; Figure 1 gives an example Center (NNDC) website at www.nndc.bnl.gov. We are using the Q value for beta-delayed neutron emission. The continually developing new tools to make data access and plots have the option for zooming in to smaller regions of visualization easier. We try to be responsive to user needs the chart or selecting a single nucleus. NuDat also can be
Figure 2. NuDat search page for making queries of specific nuclear prop- erties in ENSDF.
6 Nuclear Physics News, Vol. 27, No. 3, 2017 feature article
100 Figure 3. (Left) Previous plotting option in NuDat displaying the R4/2 ratio in a region around Mo. New plotting options are found in the middle and right panels where the same R4/2 ratio will be automatically displayed as a function of both neutron and proton number. used to search all of ENSDF for basic properties of nu- While some trends are evident, such as increasing values clei. The search page is illustrated in Figure 2, where con- as one moves away from closed shells, the fi ner details are ditions on energy, spin, parity, half-life, transition mul- not immediately obvious from the two-dimensional plot. A tipolarity and more can be placed. A particularly useful new feature in NuDat now allows observables, like the R4/2 feature in an experimental setting is the ability to search ratio, to be automatically plotted as a function of both pro- for gamma-ray transitions which are known to come in ton and neutron number. Here is where new physics can be coincidence. quickly observed, with the large gap in the plot as a func- New plotting features are currently being incorporated tion of proton number (right panel) indicating the presence into NuDat. As an example, a common observable used as of a sub-shell closure [6]. Such plotting features are avail- an indicator of deformation in nuclei is the ratio of the ex- able for a number of basic observables. For the future, more citation energy of the fi rst 4+ state to the fi rst 2+ state (the extensive plotting capabilities are being explored, includ- R4/2 ratio) in even-even nuclei. Figure 3 (left) illustrates the ing, for example, plotting one measured quantity versus previous plotting capabilities of NuDat for the R4/2 ratio. another. The traditional way of visualizing the levels in a nucleus and their decay has been to use horizontal lines to indicate excited levels and vertical arrows to indicate gamma-ray transitions. Again, in an attempt to provide users with a different perspective, the standard plotting capabilities in NuDat have been expanded to include for each nucleus the option to generate plots of excitation energy as a function of spin. An example of this type of plot is given in Figure 4 for 194Pb. The user will have the option to join individual states by their gamma-decay branching ratio, as done in Figure 4, or by transition strengths (M1, E2, etc.). In this example, the changes in shape as a function of angular momentum can be clearly identifi ed.
New Release of ENDF/B: ENDF/B-VIII.0 As mentioned above, the ENDF/B library contains Figure 4. Plot of excitation energy as a function of angular nuclear reaction data for transport and other applications. moment for levels in 194Pb. States are connected by their ENDF/B is the product of the Cross Section Evaluation branching ratios, with the width of the line proportional to Working Group (CSEWG), a collaboration that has been the intensity. active since 1967. It has been 50 years since the release of
Vol. 27, No. 3, 2017, Nuclear Physics News 7 feature article
• A new Neutron Standards evaluation • New standards-level full evaluations from the CIELO pilot project: 235, 238U, 239Pu, 56Fe, 16O, and 1H • Many new and improved neutron evaluations • New atomic reaction data • Many new thermal scattering evaluations • Improvements to charged particle reactions ENDF/B-VIII.0 is the best-performing ENDF/B library to date. ENDF/B performance is typically measured by the agreement between simulations of small zero power nu- clear reactors (critical assemblies) and their experimental realization. The fi gure of merit in these comparisons is the keff, namely the ratio of neutron gain to loss. Figure 5 shows the cumulative χ2 from a series of simulations of these criti- cal assemblies.
New Developments in Nuclear Data Sheets 2 Figure 5. Cumulative χ of ENDF/B library performance. Traditionally, nuclear structure evaluations are docu- Each tick on the x-axis represents one critical assembly mented and published in Nuclear Data Sheets (NDS), a 2 case. The y-axis is the cumulative χ comparing perfor- monthly journal published by Elsevier Science. NDS dates mance of the simulation of each critical assembly to the back to 1965 and continues to thrive and be a well-cited 2 experimental keff . Lower cumulative χ indicates better per- resource within the community. However, the format of formance. NDS has remained nearly the same for decades. Based on user input and feedback, the February 2017 issue [7] of ENDF/B-I. Currently CSEWG is preparing a new release: NDS introduces a new layout and several improvements to ENDF/B-VIII.0 the presentation of data. The most signifi cant change is in This new ENDF/B-VIII.0 Library release incorporates the presentation of tabular data. The ENSDF recommended work from across the United States and the international data are presented in two tables, one describing level prop- nuclear science community over the last six years, most no- erties and the other displaying the gamma and E0 transition tably with Europe (JEFF), Japan (JENDL), South Korea, decays. Previously, these two tables were distinct, linked and the International Atomic Energy Agency (IAEA). This only by the excitation energy of the initial level. To allow Library is being issued in the traditional ENDF-6 format, the tables to be used more independently, the gamma-ray as well as in an alternative new Generalized Nuclear Data table has been expanded, to provide the user with informa- (GND) format. ENDF/B-VIII.0 is due late 2017. tion on the spin of the parent level, as well as the excitation Major changes to ENDF/B-VIII.0 include: energy and spin and parity of the fi nal level. The font for all
Figure 6. New format of the gamma-ray table available in Nuclear Data Sheets and on-line through the ENSDF search application. New columns (indicated by the red squares) include the J π of the initial level, as well as the energy and J π of the level to which the gamma-ray decays.
8 Nuclear Physics News, Vol. 27, No. 3, 2017 feature article
over 940 citations (Google Scholar). Submissions relating to nuclear structure or reaction data are welcomed and au- thors with articles with relevance to Nuclear Data Sheets should contact the editor for additional information.
Future Outlook The history of nuclear physics has always been data driven and has shown that systematic studies of nuclear properties can lead to major advances in our understanding of how nuclei work. An exciting time is upon us, where new, modern facilities around the world are providing huge amounts of data in a new terrain of the nuclear chart. Vastly increased computing power is enabling more fundamental theoretical models based on real nuclear forces. The Internet now allows us to share these new results at unprecedented speed. With these types of advances, the rapid collection, correlation, evaluation, and dissemination of data is ever more important. The U.S. nuclear data program is eager to work closely with the nuclear physics community to ensure that all data are promptly and reliably incorporated into the databases in order to pave the way for new scientific break- Figure 7. Example of new decay drawing available online throughs. To exploit the full potential for scientific discov- and in the Nuclear Data Sheets journal. ery will also require the development of innovative soft- ware tools for display, extraction, and manipulation of the evaluated data and feedback from the users on their needs tables and text has also been increased for ease in reading. is highly requested. An example of the new gamma table is given in Figure 6. Recently, all of ENSDF was made available for download- Acknowledgments ing with this new layout and PDF format which can be ob- The authors are grateful to their colleagues within the tained at www.nndc.bnl.gov/ensdf. U.S. Nuclear Data Program and the International Network Improvements have also been made to the presentation of Nuclear Structure and Decay Data Evaluators for their of level schemes and band drawings. An example is pre- contributions to the databases and applications presented sented in Figure 7. For the sake of clarity, the requirement in this article. In particular, we thank J. Chen and B. Singh of plotting the excitation energies to scale has now been for their efforts in developing the new program for PDF relaxed, and levels are separated such that their decay is displaying of ENSDF. This work is supported by the U.S. legible. Color coding has been added, so that one can easily Department of Energy, Office of Nuclear Physics, Office of get an idea for the stronger and/or weaker transitions in the Science, under contract DE-AC-02-98CH10886. decay. Finally, decay paths involving particle emission are now incorporated into the drawings, for example, in Fig- References ure 7, the beta-delayed neutron branch is indicated by the 1. ENSDF database (Evaluated Nuclear Structure Data File), hatched region. www.nndc.bnl.gov/ensdf/ NDS is not limited to publishing just nuclear structure 2. M. B. Chadwick et al., Nucl. Data Sheets 112 (2011) 2887. evaluations. Since 2006, the journal has devoted one spe- 3. B. Pritychenko, Nucl. Data Sheets 120 (2014) 291, www.nndc. bnl.gov/nsr cial issue a year to nuclear reactions, with the aim to pro- 4. N. Otuka et al., Nucl. Data Sheets 120 (2014) 272. vide a venue for publication of key papers on reaction eval- 5. XUNDL database (eXperimental Unevaluated Nuclear Data uations that are too extensive or detailed for other journals. List), www.nndc.bnl.gov/ensdf/ensdf/xundl.jsp These issues can have a large impact, the paper detailing 6. R. B. Cakirli and R. F. Casten, Phys. Rev. C 78 (2008) 041301. the release of ENDF/B-VII.0 [8] has over 1,600 citations 7. J. Chen, Nucl. Data Sheets 140 (2017) 1. (Google Scholar), while the ENDF/B-VII.1 paper [2] has 8. M.B. Chadwick et al., Nucl. Data Sheets 107 (2006) 2931.
Vol. 27, No. 3, 2017, Nuclear Physics News 9 feature article
COSY Prepares the First Measurement of the Deuteron Electric Dipole Moment Paolo Lenisa University of Ferrara and INFN, Ferrara, Italy Frank Rathmann Institut für Kernphysik, Forschungszentrum Jülich, Jülich, Germany
One of the most intriguing questions in cosmology and Model (SM) of particle physics and thus is only able to ac- perhaps in all of physics is: “Why is there so much matter count for a tiny fraction of the actual asymmetry. in the Universe and so little antimatter?” Until today, there While particle physics at accelerators celebrated its lat- is no evidence for any primordial antimatter within our gal- est success with the discovery of the Higgs boson, culmi- axy or even beyond. There is no indication for any form of nating in a series of discoveries all consistent with the SM, co-existence of matter and antimatter in clusters or galaxies the chances have grown in recent years that new physics within our Universe. Hence, it is usually concluded that our could be at mass scales beyond the reach of current or fu- visible Universe is made entirely of matter and is intrin- ture collider experiments. This prospect, in combination sically matter non-symmetric. According to the combined with astrophysical observations (e.g., dark matter, neutrino Standard Models of cosmology and particle physics it is oscillations), not explained by the SM has stimulated in- expected that at the end of the inflationary epoch—follow- terest in high-precision physics. One such search for new ing the Big Bang—the number of particles and antiparticles physics is the quest for electric dipole moments (EDMs) in were in extreme balance, yet somehow the laws of phys- fundamental particles. ics contrived to act differently on matter and antimatter in An EDM originates from a permanent electric charge order to generate the current imbalance. Interestingly, one separation inside the particle. In its center-of-mass frame, of the necessary physics mechanisms required for such ef- the ground state of a subatomic particle has no direction at fects—namely CP-violation—is very small in the Standard its disposal except its spin, which is an axial vector, while
Figure 1. Left: Naïve representation of a fundamental particle as a spherical object with an asymmetric charge density (upper left). The particle mirror image is represented on the right, and its time-reversal at the bottom. The particle spin defines (s) a direction in space. Both P and T transformations leave the magnetic dipole moment (μ) antiparallel to the spin while change the relative orientation of the electric dipole moment (d). Therefore, the original particle can be distin- guished from its mirror or time reversal image. Right: Experimental upper limits for the EDMs of different particles (red bars) plotted together with the prediction from SUSY (blue bands) and the Standard Model (green bands). No experimental limit exists yet for the deuteron.
10 Nuclear Physics News, Vol. 27, No. 3, 2017 feature article
rad/s (about 1/100 of degree per day!). This requires the measurement to be sensitive at a level never reached before in a storage ring. These requirements imply that for a sta- tistically significant result, the polarization in the ring plane must be kept for times on the order of a thousand seconds during a single fill of the ring and the scattering asymmetry from carbon must reach levels above 10‒6 in order to be measurable within a year of running. At the Cooler Synchrotron COSY located at the For- schungszentrum-Jülich (FZJ) (Figure 3), the JEDI Collabo- Figure 2. Measuring principle of a charged particle EDM ration (http://collaborations.fz-juelich.de/ikp/jedi/index. in a storage ring. A radial electric field is applied to an shtml) is working on a series of feasibility studies for the ensemble of particles circulating in a storage ring with po- EDM experiment in a to-be-built dedicated storage ring. larization vector aligned to their momentum: the existence The COSY ring, able to store both polarized proton and of an EDM, would generate a torque that slowly rotates the deuteron beams, is an ideal machine for the development spin out of the ring plane into the vertical direction. and commissioning of the necessary technology. Following the commissioning of a measurement sys- the charge separation (EDM) corresponds to a polar vector. tem that stores the clock time of each recorded event in If such a particle possesses an EDM, it must violate both the beam polarimeter, some major achievements have been parity (P) and time-reversal (T) invariance (Figure 1, left already realized. The polarized beam is injected into COSY panel). If the combined CPT symmetry is to be valid, T vio- with the polarization vertical. Operating a radio-frequency lation also implies breaking of the combined CP symmetry. solenoid for a brief period turns the polarization into the The Standard Model predicts the existence of EDMs, but ring plane and subsequently the measurements are started. their sizes fall many orders of magnitude below the sensi- Above all, it was possible to unfold for the first time the tivity of current measurements and still far below the ex- rapid rotation of the polarization in the ring plane (~120 pected levels of projected experiments. An EDM observa- kHz) arising from the gyromagnetic anomaly. The spin tion at a much higher value might be interpreted as a sign tune (i.e., the number of spin precessions per turn) has been of new physics beyond the current Standard Model (BSM). Researchers have been searching for EDMs of neutral particles, especially neutrons, for more than 60 years, but, despite a constant increase in sensitivity, the experiments have come up only with upper bounds, nevertheless pro- viding useful constraints on BSM theories (Figure 1, right panel). More recently, a new class of experiments based on storage rings has been proposed to improve the sensitivity of the measurements and eventually be able to measure the EDM of charged particles (such as the proton, deuteron, or helion). The measuring principle is straightforward: a radial electric field is applied to an ensemble of particles circulat- ing in a storage ring with their polarization vector (or spin) initially aligned with their momentum direction. The exis- tence of an EDM would generate a torque that slowly ro- tates the spin out of the plane of the storage ring and into the vertical plane (Figure 2). This slow change in the vertical polarization is measured by sampling the beam with elas- tic scattering off a carbon target and looking for a slowly increasing left-right asymmetry in the scattered particle flux. For an EDM of 10–29 e·cm and an electric field of 10 Figure 3. The COSY storage ring at the Forschungszen- MV/m, this would happen at an angular velocity of 3·10–9 trum Jülich.
Vol. 27, No. 3, 2017, Nuclear Physics News 11 feature article
Figure 4. Achievements at the COSY Storage Ring. Left: deviation of the spin tune νs, which is defined as the number of spin precessions per turn, as a function of the number of turns in the ring. At t = 38 s (about 28 × 106 turns), the interpo- lated spin tune amounts to 16097540628.3 ± 9.7 × 10–11, which represents the most precise measurement of this quantity ever performed. Right: One of the longest polarization lifetimes recorded for the COSY ring. Measurements made at four separate times (to conserve beam) are matched to a depolarization curve that assumes a Gaussian distribution of trans- verse oscillation amplitudes. The half-life of the polarization is 1173 ± 172 s, which is three orders of magnitude longer than previous results using electron beams.
measured with a precision better than 10–10 in a cycle of 10 particles’ spin precesses with a different frequency with re- seconds that possibly represents the most precise measure- spect to the velocity, the net contribution to the polarization ment ever performed in a storage ring (Figure 4, left) [1]. It buildup coming from the motional E-fields per turn would was also demonstrated that, by determining the errors in the average to zero. The rf-Wien filter, synchronized with the polarization direction and feeding this back to make small spin precession frequency, would restore the parallelism changes in the ring radio-frequency, the direction of the po- between spin and momentum and allow the polarization larization may be maintained at the level of 0.1 radian for build-up to take place. A prototype of the radiofrequency any chosen time period. This is another requirement needed Wien filter has been successfully commissioned and was for managing the polarization in the ring for the EDM ex- tested at COSY in 2014. In the test, the B field was oriented periment. Another milestone was the achievement of polar- in the radial direction, and its force on the stored deuter- ization lifetimes in the ring plane longer than 1,000 s (Fig- ons was perfectly cancelled by the vertical electric one: the ure 4, right) [2]. Maintaining the polarization in the ring device could be used to continuously flip the vertical po- plane requires the cancellation of effects that may cause the larization of a 970 MeV/c deuteron beam without exciting particles in the beam to differ from one another. Bunching any coherent beam oscillations. In the EDM experiment, and electron cooling the beam serves to remove much of this spurious motion. However particle path lengths around the ring may differ if particles in the beam have transverse oscillations with different amplitudes. The effect of these differences on polarization decoherence may be removed by applying correcting sextupole fields to the ring. As a re- sult, the polarization lifetimes now reach the required dura- tion for the EDM experiment. In 2016 the European Research Council awarded an Advanced Research Grant to the Jülich group, supporting further R&D efforts. The goal of the project is to conduct the first ever measurement of the deuteron EDM. Since at COSY the polarization cannot be maintained parallel to its Figure 5. First measurement of the deuteron EDM as velocity, a novel device called a radiofrequency Wien filter planned at COSY. The spin precesses in the vertical mag- [3] will be installed in the ring to slowly accumulate the netic field of the dipoles and feels a torque caused by the EDM signal: the filter influences the spin motion without interaction of the EDM with the electric motional field. To acting on the particle’s orbit. The idea is to exploit the elec- allow for polarization buildup to occur, an RF-Wien filter tric fields created in the particle rest system by the mag- will be used to control the relative phase between spin and netic fields of the storage-ring dipoles (Figure 5). As the momentum.
12 Nuclear Physics News, Vol. 27, No. 3, 2017 feature article
with beams traveling in opposite directions in the storage ring. The commissioning of the RF-Wien Filter and the dem- onstration of its control over the particles’ spin will rep- resent a fundamental milestone towards the design and realization of the final high-precision ring with a EDM sen- sitivity goal of 10–29 e.cm or even better. This will neces- sarily require the use of clockwise (CW) and counterclock- wise (CCW) beams to remedy systematic errors like: radial magnetic fields, non-radial electric fields, vertical quadru- Figure 6. Concept of a dedicated ring for the measurement pole misalignments, rf-cavity misalignments and unwanted of an electrical dipole moment (proton case). Two particle field components. As a matter of fact, the main systematic beams circulate in opposite directions in a radial electric error coming from an unwanted spin precession due to the field with polarization vector aligned to their momentum: magnetic dipole moment in radial magnetic fields (which is the existence of an EDM would generate a torque that indistinguishable from the EDM signal) can be controlled slowly rotates the spin out of the plane of the storage ring to a very high accuracy in the CW-CCW scheme, as the into the vertical direction. Note that for a beam impulse very same radial magnetic field causes forces in different of p = 0.701 GeV/c (magic momentum) there is no spin directions for two opposite beams (Figure 6). precession in the accelerator plane due to the magnetic Also in view of the possible construction of a dedicated moment. EDM ring, COSY constitutes an important test facility of many EDM related key technologies. Besides polarimetry, beam position monitoring and active control systems, also the radiofrequency Wien filter will be rotated by 90° around the design of electrostatic and electromagnetic deflectors the beam axis, so that the B field will point in the verti- benefits by direct test in a storage ring. In addition, checks cal direction and consequently act on the spins of the par- for systematic errors can be undertaken for further develop- ticles precessing in the horizontal plane. To accomplish to ments and applications. the task, the frequency of the Wien filter will be locked to Recently CERN also demonstrated interest in the per- the spin motion of the particles by a novel developed spin- spectives offered by storage-ring EDM searches. An EDM feedback system. kickoff meeting took place on 13–14 March 2017 at CERN The most significant challenges will come from the and a working group has been being established to investi- management of systematic errors. Small imperfections in gate the option. the placement and orientation of ring elements may cause stray field components that generate the accumulation of an ORCID EDM-like signal. The experiment is most sensitive to radial Paolo Lenisa magnetic fields and vertical electric fields. Similar effects http://orcid.org/0000-0003-3509-1240 may arise through the non-commutativity of spurious rota- tions within the ring system. Efforts are underway to model References these effects through spin tracking supported with beam 1. D. Eversmann et al., Phys. Rev. Lett. 115 (2015) 094801. testing. Eventually, many such effects may be reduced or 2. G. Guidoboni et al., Phys. Rev. Lett. 117 (2016) 054801. eliminated by comparing the signal accumulation rates seen 3. J. Slim et al., Nucl. Instr. Meth A 828 (2016) 116.
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Vol. 27, No. 3, 2017, Nuclear Physics News 13 feature article
Searching for 0νββ Decay in 136Xe: Toward the Ton-Scale and Beyond T. Brunner Physics Department, McGill University, Montreal, QC, Canada and TRIUMF, Vancouver, BC, Canada L. Winslow Laboratory for Nuclear Science, Massachusetts Institute of Technology, MA, USA
The quest for neutrinoless double-beta decay (0νββ) is a and KamLAND-Zen experiments are searching for a 0νββ promising experimental approach to search for lepton num- decay in 136Xe. Xenon-136 has a relatively high natural ber violation in weak interactions, a key ingredient in gen- abundance of 8.6%, which makes enrichment easier, and erating the matter-antimatter asymmetry through models the Q value of 2.5 MeV is above most naturally occurring of Leptogenesis. The 136Xe-based 0νββ experiments Kam- backgrounds. LAND-Zen and EXO-200 currently set the most stringent Once observed, the effective Majorana neutrino mass limits on this process using two very different techniques.
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Phase I
Figure 2. (left) EXO-200 phase I single-site energy spectrum. The insert is zoomed in at the region around the Q value. (right) Sectioned view of the EXO-200 TPC with annotations to main features of the detector. The Teflon sheet in front of the field-shaping rings reflects scintillation light and increases the avalanche photo diodes’ (APDs) acceptance. Figures adapted from Refs. [5, 6].
The EXO and KamLAND-Zen collaborations are cur- used to fully reconstruct the energy of each event, its loca- rently developing concepts of next generation experiments tion within the detector volume, and its multiplicity, that in parallel to the operation and data taking with the current is, the number of locations at which energy was deposited detectors. Current and future developments will be pre- in each event. Beta events deposit energy predominantly sented in the following sections. in one location (single-site events), while γs scatter depos- iting energy at multiple locations (multisite events). Fig- Current Results ure 2 shows the single-site energy spectrum of EXO-200, The current half-life limits of EXO-200 and KamLAND- which is dominated by 2νββ events. The multisite spectrum ZEN were used to extract the effective Majorana neutrino (not shown) mainly consists of γ events, which are used mass-limit region using nuclear matrix elements from [3, to constrain the background models of the single-site fit. 4], which is shown as solid bands in Figure 1. Projected Alpha events mainly emit scintillation light and are easily sensitivities of EXO-200 final and KamLAND-Zen 800 are identified and discriminated. The event location allows to shown as hatched bands. KamLAND-Zen and EXO-200 optimize the sensitivity of a physics search by adjusting the currently provide two of the most stringent limits on the fiducial volume and taking advantage of the self-shielding 0νββ-decay half-life, independent of the choice of isotope. of xenon. In phase I of data taking with EXO-200, an energy reso- EXO-200 lution of 1.53 ± 0.06% at the Q value was achieved [5]. EXO-200 is a liquid xenon time-projection chamber This data set allowed the measurement of the 2νββ half life 2ν 21 (TPC) located at the Waste Isolation Plant Project (WIPP) T1/2 = 2.165 ± 0.061 · 10 years [6], which is the slowest in New Mexico, USA. The detector consists of two al- decay rate ever measured directly, and put a limit on the 0ν 25 most identical TPC halves with a shared, optically trans- 0νββ half life of T1/2 > 1.1 × 10 years at the 90% confi- parent, cathode [7], which creates two drift regions with dence level (C.L.) with a sensitivity of 1.9 · 1025 years at an a drift field of ~400 V/m. The detector is filled with 175 exposure of 100 kg-year [5]. kg of liquid xenon enriched to ~81% in the isotope 136Xe. In early 2014, two independent incidents at the WIPP A sectioned view of an engineering rendering of EXO-200 site caused the mine operation and EXO200 to halt, and is shown on the right side in Figure 2. Radioactive decays only in early 2016 EXO-200 phase II low-background data and cosmic radiation deposit energy in the detector volume, taking could resume. During this down time part of the ionizing the xenon and creating scintillation light and free detector’s front-end electronics was upgraded and a “de- electrons, which are drifted toward the anode wire planes. radonator” was installed to reduce the radon concentration Both scintillation light and electric charge are read by large- in the air gap between the outer cryostat and low-radio- area APDs and two wire planes, called u and v wires, re- active lead shielding. These upgrades along with analysis spectively. Scintillation-light and charge measurement are improvements resulted in a 2-fold increase of EXO-200’s
Vol. 27, No. 3, 2017, Nuclear Physics News 15 feature article
sensitivity to 3.7 × 1025 years and a limit on the 0νββ half self-shielding, and fully contained energy depositions can life of T1/20ν > 1.8 × 1025 years at the 90% C.L. for the make up for the relatively poor energy resolution. The Ka- full data set [19]. mLAND-Zen experiment is in the process of installing a new slightly larger mini-balloon to hold ~800 kg of 136Xe. KamLAND-Zen Data taking for KamLAND-Zen 800 is expected to start KamLAND is a monolithic liquid scintillator detector in the next year. This is the first step in KamLAND-Zen’s located in the Kamioka Mine in Japan. The original oscilla- ton-scale program, which includes a major upgrade to the tion experiment used one kiloton of liquid scintillator con- detector described in the next section. tained in a 6.5 m radius balloon to detect antineutrinos from Japan’s nuclear reactors. KamLAND-Zen uses this large scintillating volume as an active shield for a central vol- Ton-Scale Experiments ume of enriched xenon-doped liquid scintillator contained In order to make a definitive search for 0νββ in the in- in an inner balloon with a radius of 3 m. A schematic of the verted mass-hierarchy, target masses on the order of a few KamLAND-Zen detector is shown in Figure 3. tons are required. Several collaborations are developing de- The inner balloon was installed in 2011, the same year as tector concepts to probe this parameter space. KamLAND2- 136 the great east Japan earthquake and subsequent Fukushima Zen and nEXO propose to search for 0νββ in Xe deploy- power plant disaster. The first phase of data taking from ing 1 ton and 5 tons of enriched Xe, respectively. Their 12 October 2011 to 14 June 2012 with an exposure of 89.5 projected sensitivity limit is show as a cross-hatched band kg-year of 136Xe showed a significant contamination from in Figure 1. 110mAg, a fission product. A purification campaign success- fully removed this background. The post-purification phase nEXO collected data from 11 December 2013 to 27 October2015, The nEXO detector concept is based on the success of corresponding to an exposure of 504 kg-year and a sensi- EXO-200. The detector is anticipated to be deployed at 25 0ν 25 tivity of 5.6 × 10 yrs. It set a limit of T1/2 > 9.2 × 10 SNOLAB in Ontario, Canada, where the Nobel Prize–win- years and when combined with the pre-purification data set ning SNO detector was located. An artist rendering of the 0ν 26 leads to a limit of T1/2 > 1.01 × 10 at the 90% C.L. This detector is shown in Figure 4. nEXO is being designed as is the leading limit for 0νββ and KamLAND-Zen is the first a cylindrical, monolithic, single-volume, liquid xenon TPC experiment to surpass the 1026 year half-life. with a drift field of 400 V/cm deploying 5 tons of xenon en- The success of KamLAND-Zen has shown that the ad- riched in 136Xe at ~90%. A segmented anode with perpen- vantages of the liquid scintillator technique: large masses, dicular x and y channels collects the charge signal, while
Chimney Corrugated Tube 4 (a) Period-2 Data 110mAg 10 Film Pipe Total 238U+232Th+210Bi Total +210Po+85Kr+40K Suspending Film Strap 103 (0νββ U.L.) IB/External Photomultiplier Tube 136Xe 2νββ Spallation 136 ThO 2W Calibration Point 102 Xe 0νββ (90% C.L. U.L.) Xe-LS 13 ton 10 (300 kg 136 Xe) Buffer Oil Events/0.05MeV Outer Balloon Outer LS 1 kton (13 m diameter) 1 Inner Balloon (3.08 m diameter) 10−1 1234 Visible Energy (MeV) Figure 3. (left) KamLAND-Zen Energy spectrum of selected 0νββ candidates within a 1-m-radius spherical volume in Period-2 drawn together with best-fit backgrounds, the 2νββ decay spectrum, and the 90% C.L. upper limit for 0νββ decay from Ref. [8]. (right) Schematic diagram of the KamLAND-Zen detector from Ref. [9].
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that these three improvements boost the light collection ef- ficiency by factors of 1.9, 1.8, and 1.4, respectively. The improvement in energy resolution is complemented by a modest increase in the isotope mass to bring the total to 1 ton and new electronics to improve the tagging of the muon spallation background from 10C. More novel back- ground techniques involving scintillating balloon film and a secondary imaging system are also being explored. The goal of the KamLAND2-Zen phase is to reach 20 meV.
Beyond the Ton-Scale The increase in sensitivity in future 0νββ searches will Figure 4. Artist rendering of the nEXO TPC (right) and be limited by the available target mass. Advanced technolo- its installation at the SNOLAB cryopit (left). The cryostat gies may provide a path forward toward probing further into is submerged in a water tank, which acts as active shield- the normal neutrino-mass hierarchy. These technologies ing. SiPMs will be mounted between field shaping rings and must suppress β, γ and even solar neutrino backgrounds detector wall. that ultimately limit a detector’s sensitivity to 0νββ. Two approaches are presented with the potential to iden- scintillation light is recorded by Silicon Photon Multipli- tify ββ events by either probing the decay volume for the ers (SiPMs). These photon detectors are mounted outside existence of the 136Xe decay daughter 136Ba, or by applying of the field shaping rings, but inside the liquid xenon vol- directionally sensitive liquid scintillator. ume, covering the area of the cylindrical detector wall (~4 m2 area). SiPM devices sensitive to Xe-scintillation light Barium Tagging for 0νββ Searches at 175 nm are currently being developed and tested by the Ba-tagging is being developed for application in a nEXO collaboration [10]. monolithic xenon TPC and describes the following con- Simulations of nEXO, based on EXO-200 and radio- cept: when a 0νββ-candidate event is recorded, it is local- 0ν 27 assay data, predict a sensitivity to T1/2 of 9.4 · 10 years ized instantly and a small volume surrounding the event’s after 10 years of data taking. The resulting sensitivity to location is extracted from the detector volume and probed the effective Majorana neutrino mass is shown as a cross- for the presence of a Ba-ion. If a 136Ba is found, the event hatched band in Figure 1 for different matrix elements [3, is considered for the 0νββ search, otherwise it is classified 4]. This assumes an improved energy resolution of 1% at as background. This unambiguous identification of events the Q-value, which is achieved by improved light detec- at the Q-value as ββ or background events increases the tion and electronics. nEXO, like EXO-200, will fully re- detector’s sensitivity without increasing its mass, however, construct event energy, location, multiplicity, and topology. more significant is the ability to confirm an observed 0νββ This sophisticated reconstruction in conjunction with the signal as originating from true ββ-decay events. self-shielding of xenon will significantly increase nEXO’s Ba-tagging has been proposed by Ref. [11] and various sensitivity in comparison to an experiment deploying a sim- approaches are pursued by the nEXO collaboration using a ilar target mass of a different isotope in many small-volume tip or cold probe to extract 136Ba from the volume [12, 13] detectors. (see Ref. [14] for a proposed technique to identify Ba inside the detector). An alternative approach proposes to move a KamLAND2-Zen capillary close to the event location and flush the 136Ba- KamLAND2-Zen’s focus is an improvement in the en- ion out of the detector with liquid xenon. Once outside ergy resolution from ~4% √E to ~2% √E. The detector has the detector, the xenon undergoes a phase transition and a been running continuously for more than 15 years and is radio-frequency (RF) ion funnel is applied to separate ions due for a major refurbishment. As part of this work the de- from the neutral xenon gas. Following the extraction into tector will be drained and the main spherical tank will be vacuum, the Ba-ion will be captured in a linear Paul trap inspected. The improvement in energy resolution comes and identified through isotope-selective laser-fluorescence from the installation of new high quantum efficiency pho- spectroscopy. Such a system is currently being developed tomultiplier tubes with Winston cones and a higher light collaboratively by Carleton University, McGill University, yield LAB-based liquid scintillator. The R&D indicates and TRIUMF and is based on an RF ion funnel developed
Vol. 27, No. 3, 2017, Nuclear Physics News 17 feature article
Figure 5. Schematic of the setup to extract Ba-ions from xenon gas and identify them by means of laser-fluorescence spec- troscopy. Ba-ions are produced through laser-ablation at a source target located in xenon gas and extracted into vacuum by a combination of RF funnels. The mass spectrometer is proposed for systematic ion-extraction studies. Gas-flow calcu- lation courtesy of V. Varentsov.
at Stanford University. This RF-funnel allowed the extrac- sensitivity comes from installing 40 tons of pressurized tion of ions, produced by either a 148Gd α or a 252Cf fission xenon-doped liquid scintillator into the center of Super-Ka- source, from xenon gas of up to 10 bar into vacuum [15], miokande. This would be coordinated with the start of Hy- achieving for the first time ion extraction from such high per-Kamiokande. The pressurization is needed to increase pressures. In parallel, an element-sensitive fluorescent laser the xenon concentration in the mini-balloon. This allows an spectroscopy technique on Ba-ions trapped in a linear Paul increase in mass while maintaining background levels since trap has been developed and individual trapped Ba-ions most backgrounds scale with volume. The R&D has already were identified [16]. The RF-funnel ion-extraction and flu- begun both on the light yield of this pressurized xenon scin- orescent laser spectroscopy setup will be further improved tillator and on the engineering of this balloon. and combined to demonstrate the feasibility of the proposed At this size and target sensitivity, the background from approach. For future studies, the radioactive ion source will 8B solar neutrinos is non-negligible. The ability to recon- be replaced with a surface laser-ablation ion source to selec- struct the direction of the ~MeV electrons would be a pow- tively create Ba ions for extraction studies. A schematic of erful background rejection tool for both this and other back- the proposed setup is shown in Figure 5. A multi-reflection grounds and would be revolutionary for large-scale liquid time-of-flight mass spectrometer will be added to allow for scintillator detectors in general. identification of ions other than barium, which is of interest Direction reconstruction relies on the ability to sepa- for ion-extraction and ion-transport studies. rate the Cherenkov and scintillation light. The composition Significant progress has been made in the development of a liquid scintillator cocktail determines an absorption of Ba-tagging techniques; Ba-ion identification through cutoff, photons with wavelengths shorter than this wave- laser-fluorescence spectroscopy especially has achieved a length become part of the isotropic scintillation light, but sensitivity on the one to three ion level. Further efforts will photons with wavelengths longer than this cutoff propagate focus on implementing this development in a workable Ba undisturbed and retain their directional information. Ref. tagging technique, which is sensitive to individual ions in [17] showed that this separation could be obtained and tons of xenon. Ba-tagging is a great challenge, however, the the direction of ~MeV electrons could be reconstructed if 0ν significant increase in sensitivity to T1/2 and the possibil- photo detectors with ~100 ps timing were used, see Fig- ity to identify events as true ββ decays makes it a powerful ure 6. The separation is improved with red-sensitive photo tool that can be applied to a future nEXO-like detector. cathodes and scintillator emission spectra narrowed using novel wavelength shifters like quantum-dots. The CHESS Directional Liquid Scintillator experiment recently demonstrated Cherenkov/Scintillation The next step in the KamLAND program is Super-Kam- separation in an LAB-based cocktail using a bench-top ap- LAND-Zen with a target sensitivity of 8 meV. The increased paratus and cosmic muons [18]. A prototype detector called
18 Nuclear Physics News, Vol. 27, No. 3, 2017 feature article
Photon Arrival Time Reconstructed Direction
180
160 Ekin = 1.4 MeV 50 p Scintillation Light 140 x = cos(θ) 40 120 |p| 100 p 30 y 80 |p| 20 60 pz Events / 0.05 40 |p| 10 Early Cherenkov Light 20 PEs per event/0.1 ns 0 0 30 35 40 45 50 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 p /|p| Time [ns] x,y,z Figure 6. (left) Photoelectron (PE) arrival times after application for the simulation of 1,000 electrons (5 MeV). PEs from Cherenkov light (black, solid line) and scintillation light (red, dotted line) are compared. The dash-dotted vertical line il- lustrates a time cut at 34.0 ns. This is the default simulation: bialkali photocathode and TTS = 0.1 ns (σ). After the 34.0 ns time cut, 171 PEs from scintillation and 108 PEs from Cherenkov light are detected. (right) The reconstructed direction, (px/|p|,py/|p|,pz/|p|), for the simulation of 1,000 electrons. In the simulation, the electrons are produced along the x- axis, p/|p| = (1,0,0), and originate at the center of the 6.5 m-radius detector, r = (0,0,0). Only photons with arrival time of t < 34.0 ns are used in the reconstruction. The quantum efficiency of the bialkali photocathode is taken into account. The reconstruction at 1.4 MeV is shown. From Ref. [17].
NuDot is being constructed at MIT to demonstrate this 5. J. B. Albert et al., Nature 510 (2014) 229. technique on the ton-scale. 6. J. B. Albert et al., Phys. Rev. C 89 (2014) 015502. 7. M. Auger et al., Journal of Instrumentation 7 (2012) P05010. Conclusion 8. A. Gando et al., Phys. Rev. Lett. 117 (2016) 082503. [Adden- The search for 0νββ decays is an exciting quest to inves- dum: Phys. Rev. Lett. 117 (2016) 109903]. 9. A. Gando et al., Phys. Rev. C85 (2012) 045504. tigate if neutrinos are Majorana particles. Current genera- 10. I. Ostrovskiy et al., IEEE Trans. Nucl. Sci. 62 (2015) 1825. tion experiments, such as KamLAND-ZEN and EXO-200, 11. M. K. Moe, Phys. Rev. C 44 (1991) R931. are probing the degenerate hierarchy parameter space down 12. K. Twelker et al., Rev. Sci. Instr. 85 (2014) 9. to about 60 meV. With the advent of ton-scale experiments, 13. B. Mong et al., Phys. Rev. A 91 (2015) 022505. this limit will be pushed below 10 meV, hence fully prob- 14. B. Jones, A. McDonald, and D. Nygren, Journal of Instru- ing the inverted mass hierarchy. Depending on the nature of mentation 11 (2016) P12011. the neutrino, a ground-breaking discovery is within reach 15. T. Brunner et al., Inter. J. Mass Spectr. 379 (2015) 110. of next generation 0νββ detectors. It is an exciting time for 16. M. Green et al., Phys. Rev. A 76 (2007) 023404. 0νββ decay searches. 17. C. Aberle et al., JINST 9 (2014) P06012. 18. J. Caravaca et al., (2016) arXiv:1610.02011v1. Acknowledgments 19. J. B. Albert et al., (2017) arXiv:1707.08707. T. B. and L. W. acknowledge support from the EXO- 200 & nEXO, and KamLAND-ZEN collaborations, respec- tively.
References 1. V. I. Tretyak and Y. G. Zdesenko, Atom. Data Nucl. Data Tabl. 80 (2002) 83. 2. S. Dell’Oro et al., Adv. High Energy Phys. 2016 (2016) 2162659. 3. M. T. Mustonen and J. Engel, Phys. Rev. C 87 (2003) 064302. 4. T. R. Rodríguez and G. Martínez-Pinedo, Phys. Rev. Lett. 105 T. Brunner L. Winslow (2010) 252503.
Vol. 27, No. 3, 2017, Nuclear Physics News 19 facilities and methods
The Actual AMS Capabilities at the University of Cologne
Introduction alogy of the University of Cologne solid-state high voltage power supply. Accelerator Mass Spectrometry it constitutes a new center for Accel- This results in a low ripple and high (AMS) is a technique to measure erator Mass Spectrometry at the Uni- stability of the terminal voltage with- long-lived radioisotopes with very versity of Cologne called “Cologne out the need of a corona-stabilization. high sensitivity. The radioisotopes AMS” [8]. The main local research The accelerator can be operated with can be of natural origin such as cos- program is focused on applications in foil and gas stripper. Because of the mogenic nuclides produced by cosmic the geosciences. Examples are expo- absence of moving parts, except of a rays or of anthropogenic origin such sure dating of glacial moraines impor- rotating shaft driving a generator in as nuclides produced in nuclear fuel tant for global climate change studies, the terminal, dust production is rather processing or nuclear weapons tests. the investigation of fault movements low which results in very low down Since its development in 1977 AMS for tectonics and paleoseismics, and time of the machine. It is followed by has revolutionized the field of radio- the quantification of landscape evolu- the high-energy mass spectrometer. It nuclide dating. There is nowadays a tion. The Institute for Nuclear Physics consists of a 90° high mass resolving wide range of applications for AMS adds a research program in Nuclear analyzing magnet (ρ = 2 m) and two in various fields like earth and ocean Astrophysics, for example, search for 35° electrostatic deflectors before the sciences, archaeology, hydrology, 60Fe and 244Pu in lake sediment cores ions are directed into the particle de- pollution studies, biochemistry, and and more precise measurements of tectors for the rare isotope counting. biomedicine [1]. Throughout the last half-lives of radionuclides with cru- Since in AMS normally isotopic ra- years, AMS enabled investigations of cial impact on astrophysical models. tios are measured, the stable isotopes various astrophysical processes. The need to be measured too. This is done detection of supernova-produced 60Fe in Faraday cups directly after the 90° in manganese crusts [2], deep-sea res- The AMS Device at the analyzer magnet. It has to be ensured ervoirs [3, 4], and microfossils [5, 6] University of Cologne and the that the ion optical conditions for the as well as on the surface of the moon Actual Performance rare and stable isotopes are identical. [7] constrained a near-by supernovae The layout of the actual AMS This is realized by putting the cham- events approximately 2 million years system is shown in Figure 1. It was ber of the low energy 90° magnet on ago. Moreover, the high sensitivity of built by High Voltage Engineering, a high voltage potential via a fast high the AMS measurements might indi- Amersfoort, the Netherlands [9]. The voltage bouncer power supply to ad- cate multiple supernovae events in the injector consists of a low energy mass just the momentum of the stable iso- near-earth region (<100 parsec) from spectrometer with a 54° electrostatic bars to that of the radioactive isotope. 3 million to 2 million years ago [4]. analyzer (ESA) and a 90° dipole mag- The sequential injection of the differ- Due to the increasing demand for net with a bending radius ρ = 45 cm. ent beam components is repeated at a AMS measurements using cosmo- The injector is equipped with a multi frequency of 100 Hz. genic nuclides, for example, 10Be, 14C, sample negative ion sputter source A switching magnet with ports 26Al, 36Cl, 41Ca the German Research that can be loaded with up to 200 at −/+30°, −/+15°and 0° positioned Foundation (DFG) decided in 2007 to sample cathodes. The ESA of the in- downstream of the ESA allows to fund a new 6 MV high performance jector can be mechanically switched use different detector setups. The one AMS user facility. After a competition from +54° to −54° which allows to at −30° is used for 14C and 26Al for process between German universities mount two ion sources in parallel. Ac- which no stable isobar suppression and research centers, it was decided tually, the second ion source mounted is needed. At +30° a degrader foil is to install the device at the Institute for at −54° is used solely for CO2 mea- followed by a high acceptance 120° Nuclear Physics of the University of surements. The accelerator, a 6 MV magnet, which reduces isobaric beam Cologne. Together with two sample TANDETRON, uses a parallel fed components entering the ionization preparation laboratories, operated by Cockcroft-Walton generator as a chamber. For more details see Refs. the Institute of Geology and Miner- charging system equipped with an all- [8, 9].
20 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
Figure 1. Layout of the actual 6 MV TANDETRON AMS setup. Also shown are photos depicting parts of the installation (for more details see text).
Performance and Improvements Collaborative Research Centre 806, in the field of AMS including new CologneAMS started its opera- speaker A. Richter: “Our Way to Eu- techniques and detectors, ion sources, tion in 2011 and since then the num- rope, Culture-Environment Interac- and overall instrument design as well ber of measured samples increases tion and Human Mobility in the Late as the development of new nuclide steadily. Actually about 2,500 samples Quaternary.” In 2016 a new Collabor- systematics. For investigating short- are measured per year. The precision ative Research Centre 1211, speaker T. term geological processes and for very reached (Table 1) is at highest level Dunai: “Earth—Evolution at the Dry long-term processes measurements of worldwide. Scientific projects where Limit” was approved. This CRC in- 41Ca and 53Mn are used, respectively. CologneAMS contributes with AMS cludes a dedicated project for techno- The isotope 32Si is suited as a potential measurements are related to the DFG logical and methodical developments tracer for ocean circulations.
Table 1. Details on the actual AMS performance at CologneAMS for different isotopes. Precision of Terminal Current at LE-cup/ modern isotope voltage/charge transmission Reproducibility Blank ratio (for high Radionuclide state LE- to ANA-cup of standards values counting statistics) 14C 5.5 MV/4+ 40–50 µA (elect.)/50% 0.4% 1∙10–16 0.4% 14 + –15 CO2 5.5 MV/4 7–12 µA (elect.)/50% 0.8% 9∙10 5 µg—2.5% 30 µg—1% 10Be(1) 4.5 MV/2+ 2 µA (elect.)/60% 1% 1∙10–16 3% 26Al(2) 3 MV/3+ 200 nA (elect.)/36% 1% 5∙10–16 3% 36Cl(3) 6 MV/5+ 25 µA (elect.)/27% 1% 5∙10–15 3% Pu(4) 3 MV/3+ — 1% — 3% (1)Degrader foil technique with 120°-magnet (for 4+ charge state); ion extracted from source: BeO–; (2)no interferences; (3)degrader foil technique with 120°-magnet (for 10+ charge state); (4)slow sequential injection; ion extracted from source: PuO.–
Vol. 27, No. 3, 2017, Nuclear Physics News 21 facilities and methods
In addition to the routine measure- ments several new developments were made to increase the measurement capabilities and to improve the perfor- mance for specific isotopes. First the original system was enlarged by add- ing a specific detector for actinides (U, Pu) and a time of flight (TOF) detec- tion system. The second ion source is dedicated for CO2 samples (financed partly by the GFZ Potsdam within the frame of a common collaboration). It was installed in 2015 and since then optimized for high output of nega- Cultivation time [a] tive carbon ion beams [10]. Negative Figure 2. 239+240Pu activity determined from the absolute concentration of carbon ions can be extracted from the the measured 239Pu and 240Pu concentrations in soil samples of farmland in ion source with an efficiency of 5%. Tweespruit (South Africa) as a function of cultivation time. Shown are the experi- Small samples down to 3 µg can be mental values measured independently at CologneAMS and Australian National measured. This enables in-situ and University (ANU) as well as a line to guide the eye. compound specific14 C measurements. Both techniques are employed by ge- ologists who use compound specific using a known 242Pu spike material. MV Tandem accelerator consists of 14C AMS measurements to investigate Figure 2 shows the plutonium activity a double focusing 90° dipole magnet biodegradation in thawing permafrost of the examined farmland, calculated (ρ = 100 cm) followed by a multi- soils studies with the aim to estimate from the sum of the absolute concen- faraday cup unit where the stable iso- 240 239 the amount of C02 or CH4 release of trations of Pu and Pu content, as topes are measured. Further down- thawing permafrost regions [11]. a function of the years of cultivation. stream a 30° electrostatic deflector (ρ = The graph shows the expected behav- 300 cm) is positioned with a degrader Soil Erosion Studies with Pu ior caused by soil erosion. A dramatic foil in front, which can be inserted into Originating from Bomb Test fertile soil loss (>50%) is observed the beam. Further mass separation can Fallout within the first 10 years of cultivation be achieved by a second degrader foil Aside from cosmogenic nuclides activities [13]. in combination with a TOF system. actinides can be efficiently measured The rare isotopes will be registered in a at the Cologne AMS facility. The first A New AMS Setup at the multi-anode ionization chamber. Very AMS measurement of this type used 10 MV FN Tandem Accelerator soon this setup will be equipped with 239,240,242Pu isotopes in a study of soil This setup aims for AMS appli- a 135° gas filled magnet (ρ = 100 cm). erosion from sites in South Africa. cations with medium mass isotopes This magnet will be used especially The identification of the Pu origin for where isobar suppression benefits from for the measurement of 53Mn where soil samples from the farmlands of high beam energies (e.g., 32Si, 41Ca, it is crucial to suppress effectively the South Africa was determined via the 60Fe or 53Mn) [14]. Figure 3 shows the stable isobar 53Cr. 240Pu/239Pu-ratios measured in soil new setup as it will be realized in its samples. The acquired 240Pu/239Pu- final stage. It consists of a low energy Summary ratios of these samples resulted in a mass spectrometer with a multi-athode In 2011 a new center for AMS mean value of 0.181 ± 0.001, which sputter ion source (NEC) followed by (CologneAMS) became operational agrees with the adopted value of 0.180 a 90° electrostatic deflector and 90° at the University of Cologne. Since for the global plutonium fallout [12]. bending magnet with a bending radius then more than 10 000 routine mea- These samples were then used to in- ρ = 45 cm. The injector is equipped surements have been performed. New vestigate the soil erosion related to for fast sequencing injections of rare developments enlarged significantly agricultural activities. The absolute and stable isotopes. The high energy AMS’ capabilities; for example, the 14 Pu concentration was determined by mass spectrometer that follows the 10 new CO2 injector enables the mea-
22 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
Figure 3. Layout of the AMS setup at the 10 MV FN accelerator dedicated for medium mass spectroscopy. Also included are photos showing parts of the installation. surement of very small samples (down by the German Geo Research Centre 10. A. Stolz et al., Proceedings of the to 3 µg of carbon). It has been dem- (GFZ) Potsdam. Conference: ECCART-12 (2016), ac- onstrated that actinides can also be cepted. 11. A. Wotte et al., Nucl. Instr. Meth. measured with high accuracy and sen- References Phys. Res. B, submitted. sitivity using a new ionization cham- 1. C. Tuniz, W. Kutschera, and D. Fink, 12. Ken O. Buesseler, J. Environ. Radio- ber. Currently, a new AMS setup at the Accelerator Mass Spectrometry (CRC act. 36 (1997) 69. 10MV FN Tandem accelerator is be- Press, Boca Raton, FL, 2009). 13. H. Wiesel, PhD Thesis, University of ing installed that is dedicated for me- 2. K. Knie et al., Phys. Rev. Lett., 93 Cologne (2013). dium mass isotopes. It will be finished (2004) 17. 14. M. Schiffer et al., Proceedings of the 3. C. Fitoussi et al., Phys. Rev. Lett. 101 Conference: ECCART-12 (2016), ac- in 2017. This setup will provide the cepted. opportunity to perform 60Fe and 53Mn (2008) 121101. 4. A. Wallner et al., Nature 532 (2016) AMS measurements that will be used 69. in astrophysical as well as in geosci- 5. P. Ludwig et al., PhD thesis, TU Mu- ence projects. nich (2015). 6. S. Bishop and R. Egli, Icarus 212 Acknowledgments (2011) 960. This work was supported by the 7. L. Fimiani et al., Lunar Planet. Sci. German Research Foundation (DFG) Conf. 45 (2014) 1778. 8. A. Dewald et al., EPJ Web of Confer- under Contract No. ME1169/19-1, and ences 63 (2013) 03006. partly by the University of Cologne in 9. M. G. Klein et al., Proceedings of the Alfred Dewald the frame of the excellence iniciative Conference: ECAART-10, Athens Institute for Nuclear Physics, “Emerging Groups,” ULDETIS, and (2010). University of Cologne
Vol. 27, No. 3, 2017, Nuclear Physics News 23 facilities and methods
PANDA: Strong Interaction Studies with Antiprotons
The Antiproton Anihilation in gies where the coupling constant αs is tions. Open and hidden charm, lepton Darmstadt (PANDA) collaboration at small and perturbation theory is appli- pairs and radiative channels, hidden the Facility for Antiproton and Ion Re- cable. However, at low energies, the strangeness and hyperons, are com- search (FAIR) is a cooperation of more theory becomes strongly coupled as mensurable probes to explore the im- than 400 scientists from 19 countries. αs becomes large. In this non-pertur- minent questions among bound states FAIR will be an accelerator facil- bative regime, it is still hard to make of QCD. ity leading the European research predictions from fi rst principles. Fur- “Why antiprotons?” is asked fre- in nuclear and hadron physics in the thermore, complex systems of quarks quently. The answer lies in the advan- coming decade. It will address a wide and gluons are strongly coupled many- tages antiprotons have in the produc- range of physics topics in the fi elds body problems. tion of a rich variety of hadrons with of nuclear structure, nuclear matter, The complexity of many-body sys- respect to other experimental probes atomic, and plasma physics. Several tems in non-perturbative QCD gives and the fl avor-blindness of the well- topics in applied science and accelera- rise to many questions: What are the defi ned initial states, which is comple- tor development will be addressed as effective degrees of freedom that sys- mented by the unique feature of high well. FAIR builds on the experience tematically describe resonances and precision mass scanning. and technological developments from bound states? Where are the exotic An important feature of the new an- the existing GSI facility, and incor- resonances and bound states predicted tiproton facility is the combination of porates new technological concepts, by QCD? How do bound quark sys- phase-space cooled beams and dense such as rapidly cycling super-conduct- tems interact? What is the residual internal targets, comprising challeng- ing magnets. structure of the hadronic systems? ing beam parameters in two operation The existing GSI accelerators will Thus, the central goal of the PANDA modes: a high-luminosity mode with be upgraded and complemented by a experiment is the elementary under- beam intensities up to 1011 in a later proton-linac to be used as injectors for standing of hadrons using the power stage, and a high-resolution mode with the newly built complex of synchro- of an antiproton beam on hydrogen or a momentum spread down to a few trons and storage rings to form FAIR. nuclear targets. times 10−5 and beam intensities up to This facility will provide intense sec- The annihilation of antiprotons has 1010. A powerful stochastic cooling ondary beams of antiprotons and rare proven in the past to be a universal system will be employed to meet the isotopes, which will be used for the tool for carrying out such investiga- experimental requirements. The High research at the experimental setups. It is sometimes said that the whole is more than the sum of its parts. For the proton, this expression is literally true. The sum of the masses of its va- lence quarks account for less than 2% of the proton’s total mass, with the rest resulting from the kinetic and binding energies among quarks due to dynam- ics of the strong interaction. The ac- cepted theory of the strong interaction is quantum chromodynamics (QCD). It describes the properties of quarks and their interactions through glu- ons, the force mediator of the strong Figure 1. High Energy Storage Ring at FAIR. The PANDA detector is located interaction. QCD is very successful in one of the straight sections where the antiproton beam interacts with a fi xed in predicting processes at high ener- target.
24 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
due to the pioneering work of Gell- Mann as being composed of quarks that interact with each other via the exchange of gluons. Baryons are had- rons consisting of three quarks, and mesons are hadrons consisting of an antiquark–quark pair. The fi eld of hadron physics was fragmented over decades, according to the questions under investigation and subject to the methods and tools used, into the branches of spectroscopy, structure, and interactions of hadrons. While specialized experiments have been dedicated to each of those subfi elds over the past 20 years, the PANDA experiment has been espe- cially designed together with the ac- celerator to address open and burning questions from all the subfi elds and Figure 2. Some of the many accessible hadron species with PANDA and HESR. beyond. The PANDA experiment features a Energy Storage Ring (HESR) is fi lled experiences and successes of previous modern multipurpose detector (Figure by the Collector Ring (CR), which ac- generations. 3). The combination of a high-quality cumulates by stacking the antiprotons The availability of accelerators and antiproton beam at the HESR, an un- every 10 seconds from the collision detectors like the bubble chambers led precedented annihilation rate, and a of 2.5 × 1013 protons of 29 GeV in a to a prosperous time in particle phys- sophisticated event fi ltering, is an ideal 50 ns bunch on the production target. ics in the 1950s and 1960s with the experimental infrastructure to address The HESR lattice is designed as discovery of many new particles. The important questions to all aspects of a racetrack-shaped ring, consisting vast majority of these particles came this fi eld by collecting large statistics of two 180° arc sections connected to be understood, at least qualitatively, and high-quality exclusive data to test by two long straight sections. One straight section will mainly be occu- pied by an electron cooler at a later stage and will host smaller experi- ments for nuclear and atomic physics with ion beams. The other section will host RF cavities, injection kickers, septa (Figure 1), and the installation of the PANDA experiment with an internal target. For stochastic cooling, pickup and kicker tanks are located in the straight sections, opposite to each other. The momentum of the antipro- tons ranges from 1.5 to 15 GeV/c, al- lowing for a wide variety of physics channels (Figure 2). The PANDA experiment belongs to the third generation of hadron physics Figure 3. CAD drawing of the PANDA detector, currently under construction experiments, hereby building on the and to be completed and commissioned in 2024.
Vol. 27, No. 3, 2017, Nuclear Physics News 25 facilities and methods
1000 contribute to this field in two unique pp → ΛΛ ways: (a) in explorative studies in 100 0 → ΛΣ + c.c. many-body experiments to search for → Σ− Σ+ 10 → Σ0 Σ0 high-spin and spin-exotic states and b]
µ + − (b) by a precision measurement of the
[ → Σ Σ
0 0 σ 1 → Ξ Ξ mass and width (or more generally the → Ξ+ Ξ− line-shapes) of any neutral charmo- 0.1 0 ΛΣ ΣΣ ΩΩ Λ Λ ΛΛ ΞΞ c c nium-like state. The very small mo-
0.01 mentum spread of the antiproton beam 1.4 1.5 1.6 1.7 1.8 1.9 2 2.1 2 4 6 8 10 12 14 allows a determination of the width, p momentum [GeV/c] for example of the X(3872), with an Figure 4. High antihyperon–hyperon production cross-sections in antiproton– accuracy of 50 keV. Such an accuracy proton annihilations. will provide a decisive measurement QCD in the non-perturbative regime. of antibaryons in nuclei provides a on the nature of the narrow X(3872). In the following, we will outline a few unique opportunity to elucidate strong This technique can also be used to of the physics aspects that will be ad- in-medium effects in baryonic sys- investigate excitation curves of open- dressed using this facility (see Refs. tems. Quantitative information on the charm final states, like, for example, [1, 2] for more details). antihyperon potentials will be obtained DsDs0*(2317) to measure the width of PANDA will copiously produce an- for the first time via exclusive antihy- the respective Ds0*(2317). tihyperon–hyperon pairs through the peron–hyperon pair production close to Furthermore, antiproton annihila- reaction p̅ p → YY̅ . The energy scale its production threshold in antiproton– tions allow for the study of a rich va- is given by the mass of the strange nucleus interactions. After pioneering riety of nucleon structure observables 2 in large (partly) unexplored areas such quark (ms ~ 100 MeV/c ), which is studies of the Λ potential during the below, but near the strong coupling first phase of PANDA, the Ξ and even as the kinematical regime that cor- responds to the time-like (positive, scale ΛQCD. This corresponds to the Ω potential can be explored once the confinement domain, where our the full luminosity is available. Bary- s-channel) momentum transfer of the knowledge of the strong interaction ons with strangeness embedded in virtual photon. The electromagnetic is scarce. Therefore, the relevant de- the nuclear environment, hypernuclei, form factors of the proton, transition grees of freedom—quarks and gluons or hyperatoms, are the only available distribution amplitudes (TDA), wide or hadrons—remain unclear. Spin ob- tool to approach the many-body as- angle compton scattering (WACS), servables have been proven to be very pect of the three-flavor strong interac- and Drell-Yan processes for access- sensitive to the underlying degrees of tion. As an example, high resolution ing transition momentum-dependent freedom of the model describing the γ-spectroscopy of excited states in sev- parton-distribution functions (TMD- interaction. The high cross-section for eral doubly strange ΛΛ-hypernuclei PDF) are examples of those variables. hyperon pair production using anti- will be performed for the first time. Figure 5 shows how crossing symme- proton interactions (see Figure 4) will Hypernuclear studies would result also try, for example, connects space- and provide the necessary high statistics to in valuable insights to astrophysics as time-like regions. access spin observables with sufficient well, such as the Hyperon-puzzle of The main objectives of the design of precision. In addition, so far unmea- neutron stars and mechanisms of core- the PANDA experiment are to achieve sured multi-strange hyperons are ac- collapse supernovae. almost 4π acceptance, high resolution cessible with PANDA. In particular, The field of charmonium spectros- for tracking, particle identification and seven polarization parameters of the copy is an exciting field with many calorimetry, high-rate capabilities, and spin 3/2 Ω hyperon can be extracted discoveries in the past 15 years. Many a versatile readout and event selection. for the first time. predicted states have not been ob- To obtain a good momentum resolu- This large production cross-section served and, on the other hand, masses, tion, the detector will be composed will also enable several innovative widths, and decay rates of many unex- of two magnetic spectrometers: the studies of systems containing two or pected states (XYZ states) have been Target Spectrometer (TS), based on even more units of (anti)strangeness measured. Until today, a coherent a superconducting solenoid magnet in antiproton–nucleus collisions at the picture cannot be drawn from what is surrounding the interaction point, for PANDA experiment. The interaction available experimentally. PANDA will particle tracks at large angles and the
26 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
Figure 5. Crossing symmetry relates electromagnetic scattering off the proton to, for example, lepton and photon pair production from antiproton–proton annihilations (elm FF = electromagnetic form-factor, GPD = generalized parton dis- tribution, GDA = generalized distribution amplitudes, Mh = hard process amplitude, DA = distribution amplitude, see Refs. [1, 3] for more details).
Forward Spectrometer (FS), based endcap (145° to 170°) and consists of fi cation. A Shashlyk-type calorimeter on a dipole magnet, for small angle about 16,000 PbWO4 crystals provid- with an energy resolution of 3%/√E is tracks. In both spectrometer parts, ing an energy resolution of 1.5%/√E, followed by the Muon Range System tracking, charged-particle identifi ca- whereby E is given in units of GeV. for muon detection. At the forward tion, electromagnetic calorimetry, and Particle identifi cation of pions, kaons, end, the Luminosity Detector uses muon identifi cation will be available and protons will utilize information elastic scattering of antiprotons on to allow detection of the complete from a time-of-fl ight system (ToF), a protons to determine the interaction spectrum of fi nal states relevant for cylindrical Detection of Internally Re- rate measuring antiprotons defl ected the PANDA physics objectives. fl ected Cherenkov (DIRC) light, and a at low angles. A detailed description The TS has a typical onion-like forward Disc DIRC detector. The ToF of the PANDA detector and its com- structure, very much like the detec- will use scintillating tiles with Silicon ponents can be found at Ref. [4]. tors used for the B-Factories Babar Photomultiplier readout. The cylin- As the detector response of back- and Belle: A cluster jet or pellet target drical DIRC is a bar-type DIRC with ground events is very similar to that of system will be used to provide either a quartz-prisms, while the Disc DIRC the decay of the exotic states, the use cluster beam of a target gas or frozen uses large quartz plates. The solenoid of a conventional triggered readout hydrogen pellets. Thin foils or noble magnet will provide a homogeneous scheme, where a limited number of gasses will be used for antiproton- magnetic fi eld up to 2 T in the beam subdetectors generates a trigger signal nucleus studies. The interaction point direction. The segmented yoke is in- that engages the readout of the com- is surrounded by the Micro Vertex De- strumented with chambers for muon plete detector, is not practical. There- tector (MVD) which has a vertex res- identifi cation. fore, a new type of intelligent readout olution of about 50 μm in transverse The FS covers polar angles below is being developed, where kinematical and 100 μm along the beam direction. 10° horizontally and 5° vertically. constraints are imposed online on re- Surrounding the MVD, the Straw Tube Charged particles will be detected constructed events. This technique is Tracker and Gas Electron Multiplier using the Forward Tracking System, dubbed as “triggerless readout” and (GEM) stations will be used for track- which consists of multiple straw tube allows adjusting the data selection to ing charged particles (∆pT/pT = 1.2%) layers, in conjunction with a dipole numerous physics channels. A data in the magnetic fi eld. Photons and magnet with variable fi eld depending reduction factor of up to ~103 is ex- the energy of electrons will be re- on the incident antiproton momentum. pected to be achieved by employing constructed with the Electromagnetic The momentum resolution for tracks this technique for the whole detector, Calorimeter (EMC). The EMC con- above 1 GeV/c is better than 1%. A resulting in a data rate of ~104 events/s sists of a barrel (azimuthal angle 22° Forward ToF and an aerogel-based (or, equivalently, 200 MB/s) that will to 140°), a forward endcap (down to Ring Imaging Cherenkov Counter then be sent to storage for offl ine pro- the opening for the FS) and backward detector will provide particle identi- cessing and analysis.
Vol. 27, No. 3, 2017, Nuclear Physics News 27 facilities and methods
Besides the foreseen advances in References detector technology and data treat- 1. M. F. M. Lutz et al., Physics Perfor- ment, also the theoretical develop- mance Report for PANDA: Strong ments that go hand-in-hand with the Interaction Studies with Antiprotons, experimental developments will lead arXiv:0903.3905 (2009). to new and deep insights into the dy- 2. M. F. M. Lutz et al., Nucl. Phys. A948 (2016) 93. https://doi.org/10.1016/j. namics of the strong interaction. The nuclphysa.2016.01.070 insights that PANDA will gain in the 3. U. Wiedner, Prog. Part. Nucl. Phys. fi eld of QCD might have far-reaching 66 (2011) 477. doi:10.1016/j.ppnp. TOBIAS STOCKMANNS implications to other fi elds of physics 2011.04.001 FZ Jülich as well, in particular for those in which 4. https://panda.gsi.de similar non-perturbative phenomena take place (wide range reaching from string theory to weather phenomena). The study of non-perturbative phe- nomena in a systematic way is feasible only in hadron physics. This supple- ments the long list of features that can be addressed with PANDA. GSI has a distinguished history of having made important contributions KLAUS PETERS to the physics of the strong interac- GSI Darmstadt; JOHAN MESSCHENDORP tion, in particular in the fi eld nuclear Goe the University Frankfurt KVI-CART Groningen physics. FAIR will be built on these foundations and the proposed PANDA experiment plays a complementary role, providing a link between nuclear and hadron physics. The construction of the PANDA detector has started and in-situ commissioning of the ini- tial setup is scheduled for 2024, while early physics with an antiproton beam is expected in 2025. LARS SCHMITT FAIR
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28 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
Twenty Years of VERA: Toward a Universal Facility for Accelerator Mass Spectrometry
Introduction 68Zn, 129Xe, and 202Hg, respectively. ored in red and blue) would require a With Accelerator Mass Spectrom- Sometimes it helps to start with nega- more involved isobar suppression. etry (AMS) ultra-low isotopic abun- tively charged molecular ions (e.g., Some time ago, exploratory experi- –12 –16 41 ̶ 41 dances (10 to 10 ) of long-lived CaH3 , because KH3 does not form ments at the 14-MV Pelletron tandem radionuclides, both natural and an- negative ions). In cases where stable accelerator of the Weizmann Institute thropogenic, are being measured by isobar interferences persist because demonstrated that the interaction of including an accelerator. Direct atom they also form negative ions, a separa- a laser with negative ions (anions) counting results in an enormous gain tion can be performed after accelera- could in principle solve this problem in detection sensitivity for long-lived tion with methods common to particle [3]. This worked for cases where the radionuclides as compared to their identification in nuclear physics. Here, binding energy (EA = electron affin- rare decay. For the most-used radio- higher energy helps and larger tandem ity) of the extra electron of the un- nuclide, 14C (half-life = 5,700 yr), this accelerators with terminal voltages in wanted isobaric ion is smaller than the means that instead of grams of carbon the multi-MV range are useful. On the one of the wanted one. For example, required for beta counting one can use other hand, very small tandem accel- the photodetachment of the electron milligrams or even micrograms to de- erators have been developed (TV = from negative sulfur ions (EA = 2.08 14 termine the C content. In addition, 0.2 – 0.5 MV) [1], which allow one eV) was achieved with photons of an AMS measurement takes less than to measure those radionuclides, which 2.33 eV (i.e., photons from a 532 nm an hour rather than the several days re- have very little background from Nd:YAG laser). These photons did not quired for beta counting. The gain be- stable isobars. This includes also the affect negative chlorine ions (EA = comes even larger for longer half-lives actinides, were no stable isobars exist. 3.61 eV), thus making a measurement in the million-year range and beyond. of 36Cl without interference from 36S Multiple filtering is the chief task possible. However, a very low duty of AMS in order to identify and count The Vienna Environmental factor due to the use of a pulsed laser very rare radionuclides in the pres- Research Accelerator (VERA) (10 ns pulse length at 30 Hz repetition ence of many orders of magnitude VERA is a dedicated facility for rate), made the method impractical for higher background. This comprises AMS based on a 3-MV Pelletron tan- AMS measurements. analysis by electric and magnetic dem accelerator, and has been opera- The development of isobar sup- fields, molecular dissociation, and tional at the University of Vienna for pression by photodetachment in a gas- Z identification in suitable detector 20 years. filled radio-frequeny quadrupole ion systems (Figure 1). Almost all AMS Early on, the goal was to develop guide at Oak Ridge National Labora- facilities around the world are based VERA into an AMS facility for “all” tory [4] was an important step toward on tandem accelerators [1]. This has isotopes, but this was originally re- an efficient laser–anion interaction the advantage of starting with nega- stricted to radionuclides where no system. At VERA, we have recently tively charged ions, which cannot be stable isobar interference exists (see developed our own system based on formed by certain stable isobars—the above), with the exception of 10Be and this principle [5]. This laser–anion main background for radionuclide later 36Cl. Even though these radionu- interaction system has now been cou- detection. For example, 14C ̶ is free clides allow for a large range of appli- pled to the injector of the VERA AMS from 14N interference, because ni- cations of AMS [2], many more would system (Figure 1). trogen does not form stable negative be of interest if the isobar interference The new VERA setup allows one to ions. The intense molecular isobars, problem could be solved in a more explore AMS measurements of a vari- 12 ̶ 13 ̶ CH2 and CH , break up in the ter- general way. Figure 2 displays the ety of new isotopes. In a first AMS ex- minal stripper (Figure 1). Similarly, whole family of long-lived radionu- periment, we studied the suppression the radionuclides 26Al, 55Fe, 68Ge, clides, which are of interest for AMS of 36S ̶ and 26MgO ̶ with 532 nm laser 129I, and 202Pb are free from stable- measurements. The figure shows that photons for a 36Cl and 26AlO ̶ detec- isotope interferences of 26Mg, 55Mn, about half of the radionuclides (col- tion. In both cases a dramatic suppres-
Vol. 27, No. 3, 2017, Nuclear Physics News 29 facilities and methods
Bending Magnet 90° 2 Vienna Environmental Research Accelerator ME/q = 8.3 MeV amu r = 0.350 m status 2017 Laser setup Cs-Beam Sputter RFQ Ion Beam Attenuator I on Focus Source1 Source for ion cooler x/y-Slits L aser 40 Samples I nter- Negative Ions x-Slits 75 kV Preacceleration 30kV Preacceleration A ction Ion Beam Attenuator Focus x/y-Steerer M ass x/y-Slits x/y-Steerer Electrostatic Analyzer Source2 S pectrometry E/q = 90 keV r = 0.300 m Electrostatic Analyzer 40 Samples
E/q = 60 keV r = 0.300 m Einzel Lens Einzel Lens Beam Switch y-Steerer x/y-Slits Power meter x/y-Slits Magnetic Quadrupole Wienfilter Doublet + 3 MV Tandem Accelerator ε xB = 35 kV/cm x 0.4 T Analyzing Magnet x-Slits 2 Multi Beam Switcher ME/q = 176 MeV amu r = 1.270 m Injection Magnet 2 ME/q = 17 MeV amu Offset x/y-Steerer x/y-Steerer Charging r = 0.457 m Faraday Cups Gas + Foil x/y-Slits Chain Electrostatic Einzel Lens Stripper y-Steerer Quadrupole Triplet
E-Detector Offset Faraday Cups TOF-Detector Magnetic Quadrupole Heavy Isotope Detection x/y-Slits Triplet Stable Isotope y-Steerer Measurement Experimental Station Analyzing Magnet 36 2 x/y-Slits Cl Detection ME/q = 176 MeV amu
r = 1.270 m 14 26 ∆E/E-Detector C, Al Detection 10Be Detection Ion Production and Detection x/y-Slits Electrostatic Analyzer Electrostatic Components SiN absorber E/q = 4.4 MeV r = 2.000 m Magnetic Components +∆E/E-Detector Beamline Magnetic Beam Profile Monitor PIXE - ART Switching Quadrupole ∆E/E-Detector Insertable Faraday Cup Magnet Doublet with
B = 1.66 T x/y-Steerer Figure 1. Schematic layout of the VERA AMS facility in its current configuration. The original facility became operational in 1997, and has since gone through several upgrades in order to accommodate “all” isotopes.
sion of the stable isobars by up to 1010 and AMS with its ultra-low atom Department of the Natural History orders of magnitude was observed. In counting sensitivity makes it possible Museum of Vienna. Our 14C measure- order to expand this method to other to use these radionuclides as prox- ments revealed an age of 34,000 years radionuclides, one has to know the re- ies for processes in a variety of fields for this object [6], contributing to the spective electron affinities of atomic [2]. To demonstrate the versatility of questions of the first appearance of and/or molecular anions. This informa- VERA, we discuss a few highlights anatomically modern humans in Cen- tion is currently incomplete and needs from the work during the past 20 years. tral Europe. to be investigated. Tunable lasers will In the framework of a 10-year col- allow us to measure electron affinities Archaeology laboration with archaeologists and of hitherto unknown anion species, in Because very little sample material Egyptologists we studied the Synchro- order to find those which are most suit- is needed for a 14C AMS measure- nisation of Civilisations in the Eastern able for isobar suppression. ments, precious objects can be dated. Mediterranean in the Second Millen- Thus, we were allowed to take small nium BC (SCIEM 2000 project). For Some AMS Applications at VERA samples from the teeth of a human this project we performed extensive Both cosmogenic and anthropo- skull, which was found more than 14C dating at a site in the Nile Delta, genic radionuclides penetrate many 100 years ago in a cave in Moravia which is crucial to establish an abso- sections of our environment at large, and preserved in the Anthropology lute chronology in the Late Bronze
30 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
Radionuclides for AMS (half-life in Myr) 243Am (7.4x10-3) Now possible at VERA tandem (3 MV) 240Pu (6.6x10-3) Large tandem facilities required (14 MV) 239Pu (2.4x10-2) Isobar separation presently impossible 208Bi (0.37) 237Np (2.1)
202Pb(5.3x10-2) 244 154Dy (3.0) 186mRe (0.2) Pu (80) 242 146Sm (68) Pu (0.38) 236 137La (6x10-2) 233U (0.16) U (23.4) 94Nb (2x10-2) 135Cs (2.3) 205Pb (17.3) 210mBi (3.0) 92Nb (36) 107Pd (6.5) 182Hf (8.9) 68Ge (7.4x10-7) 150Gd (1.8) 55Fe (2.7x10-6) 129I (15.7) 126 53Mn (3.7) Sn (0.22) 99 41 Tc (0.21) Ca (0.10) 93Zr (1.6) 36 Cl (0.30) 79Se (0.38) number 10Be (1.4) 60Fe(2.1) 26
Al(0.72) proton 14C(5.7x10-3) neutron number Figure 2. Display of radionuclides which are of interest for AMS measurements. Half-lives are given in brackets in units of million years. The green color marks radionuclides that can be measured at smaller AMS facilities like VERA, whereas those that can currently only be measured at larger facilities are marked in red. The ones marked in blue require special isobar suppression, which at VERA will be accomplished with the new laser–anion interaction region (Figure 1).
14 ‒ Age [7]. In this case a difference of ferred this C excess to the biosphere The Negative Hydrogen Molecule, H2 120 years was found between the time and the oceans. This created the so- The formation of first stars in the scale established by 14C dating and called 14C bomb peak with a rapidly early universe requires the formation 14 by archaeological reasoning, respec- changing C signature in the second of H2 molecules for cooling, and one tively. A similar difference shows up half of the 20th century (see inset (a) of the possible pathways is the reac- ‒ ‒ ‒ for the date of the famous volcanic in Figure 3). Among the applications tion H + H → H2 → H2 + e . The ‒ eruption of Santorini in the Aegean resulting from this unique signature, first prove of the existence of H2 with around 1600 BC. Great efforts are on the retrospective determination of the a minimum lifetime of a few micro- the way to resolve this persistent dis- birth date of cells in the human brain seconds was demonstrated at VERA crepancy, with evidence emerging that by a group of cell biologists at the Kar- through the simultaneous detection of the archaeological time scale probably olinska Institute in Stockholm stands the two protons after the dissociation ‒ needs some correction to arrive at a out [8]. In a collaboration with this of H2 in the terminal stripper of the consensus with the 14C chronology. group, we measured 14C in the DNA tandem accelerator [10]. In a collabo- extracted from neurons in the olfactory ration with the Weizmann Institute in ‒ The Ugly and the Beautiful: bulb [9], with no indication for neuro- Rehovot, the lifetime of H2 was de- The 14C Bomb Peak genesis (see inset (b) in Figure 3). This termined to be 8 µs with an ion trap In the early 1960s, the 14C content investigation required 14C AMS mea- experiment [11]. Coulomb explosion of the atmosphere sharply increased surements in carbon samples of only a experiments at the Max Planck Insti- through the intense postwar nuclear few micrograms. Later the Stockholm tute in Heidelberg revealed a high-an- weapons testing program of the su- group found a finite renewal of neu- gular momentum inter-nuclear wave per powers. After the nuclear test ban rons in the hippocampus, one of the function of this molecule [12]. These treaty of 1963, the CO2 cycle trans- most important parts of our brain. results will have some bearing on the
Vol. 27, No. 3, 2017, Nuclear Physics News 31 facilities and methods
description of the complex molecular X-ray emission (PIXE) spectroscopy layer and in the silver point material processes in the early universe. experiments at VERA for four origi- did not allow, however, for solving the nals silver point drawings from the Al- question whether the more advanced PIXE of Silver Point Drawings of bertina Museum in Vienna [13]. These drawing of Dürer’s father was actually Albrecht Dürer comprise the earliest self-portrait of a self portrait of his father or made by Among the work of the famous Dürer when he was only 13 years old the young Dürer himself. More ana- renaissance painter Albrecht Dürer (1484), and also a portrait of his father lytical work is necessary to come to a (1471–1528) are silver point drawings from two years later. A striking differ- conclusion on this interesting question. that have been investigated with vari- ence between the two drawings was ous analytical techniques by a group the ground layer, consisting mainly of Multi-Actinide Analysis of scientists at the Louvre Museum bone white for the former, and a large At VERA we developed AMS in Paris. In a collaboration with this admixture of lead white for the latter. measurements for the simultaneous group, we performed proton induced Trace element analysis in the ground analysis of very low concentrations of
Cosmic rays (p)
Atmosphere (N, O, Ar)
n 14N → 14C + p n
O2
14 CO2
Plants + Oceans (14C)
Biosphere (a) (b) (14C)
Figure 3. Picture of the first hydrogen bomb test of the United States in 1952. The simplified reaction schematic indicates that neutrons from the bomb tests convert 14N into 14C, just like the neutrons emerging from the spallation of atmospheric 14 12 nuclei with high-energy protons from cosmic rays. This led in 1963 to a doubling of the C/ C ratio in atmospheric CO2, creating the “14C bomb peak” shown on the inset (a). Here, the 14C content of DNA extracted from cells of a human who lived in the second half of the 20th century allows one to retrospectively determine the birth date of the respective cells. Adapted from [8]. Inset (b) demonstrate that neurons of the olfactory bulb from five individuals born before the bomb peak do not show any excess 14C, signaling the absence of forming new neurons after birth. Adapted from [9].
32 Nuclear Physics News, Vol. 27, No. 3, 2017 facilities and methods
292 122 Search for SHE nuclides in Nature Eka-Th Positive evidence from ICP-SF-MS: < 4 × 10-15 120 Marinov et al., Jerusalem, 2007, 2009, 2010 Upper limits from AMS: ~ 1 × 10-12 Og 118 Lachner et al., Munich, 2008 Dellinger et al., VERA, 2010, 2011 Ts Ludwig et al., Munich 2012 Lv -13 Mc < 5 × 10 Fl < 6 × 10-14 Nh < 7 × 10-16 < 3 × 10-16 < 2 × 10-15 (1-10) × 10-10
211,213,217,218Th: (1-10) x 10-11, <8 x 10-15 Figure 4. Summary of the results for searches of SHE nuclides in terrestrial materials [16], depicting the upper end of the chart of nuclides. The shades of grey in the background indicate the relative stability of nuclides due to shell model cor- rections (darker means more stable). Nuclides marked in orange have been measured with AMS. Abundance limits with respect to the corresponding host material (e.g., Rg isotopes (Eka-Au) were searched for in gold nuggets) are given in the violet boxes. The positive evidence of the Marinov experiments is shown in the blue boxes. References to the various experi- ments indicated in the top-left insert can be found in Ref. [16].
233,236U, 237Np, 239,240,242Pu, 243Am, tion sensitivity below ppq (10–15) was ciently close in time and distance, and and 248Cm from ground- and seawa- reached for some of the radionuclides. with reasonable assumptions about ter samples [14]. This method does With proper normalization with a their frequency, one expects that not require an elaborate chemical pre- multi-actinide standard, a quantitative some of the synthesized and ejected separation of the different elements, assessment of radionuclide migra- 244Pu nuclides end up in slowly accu- and is thus particularly useful for fi eld tion in natural environments has been mulating archives on Earth. We have studies of actinide migration in natu- achieved [14]. investigated deep-sea manganese ral rock formations. In collaboration crusts for such signals, and found ap- with the Institute for Nuclear Waste Live 244Pu on Earth proximately a factor of 10 less 244Pu Disposal of the Karlsruhe Institute The longest-lived plutonium iso- nuclides than expected from super- of Technology (KIT), such measure- tope is the neutron rich nuclide 244Pu, novae production [15]. Our results ments were performed for the Col- with a half-life of 80 million years indicate that 244Pu may have been loid Formation and Migration (CFM) (Figure 2). It can only be produced in produced in rare binary neutron star project at the deep underground rock stellar environments with very high mergers, an alternative stellar envi- laboratory of the Grimsel Test Site neutron fl uxes, possibly in superno- ronment for high-neutron-fl ux syn- (GTS) in Switzerland. A concentra- vae. For such events that are suffi - thesis of heavy nuclides. Theoretical
Vol. 27, No. 3, 2017, Nuclear Physics News 33 facilities and methods
consideration support such an exotic Conclusion 9. O. Bergmann et al., Neuron 74 (2012) astrophysical scenario. In 1977, accelerator mass spec- 634. trometry was introduced at Berkeley, 10. R. Golser et al., Phys. Rev. Lett. 94 Search for Superheavy Elements in Rochester, and McMaster University (2005) 223003. Terrestrial Materials [2]. Therefore in 2017 the 40th an- 11. O. Heber et al., Phys. Rev. A 73 (2006) 060501(R). Some 50 years ago, a neutron-rich niversary of AMS will be celebrated 12. B. Jordon-Thaden et al., Phys. Rev. “island of stability” beyond the heavi- at the tri-annual AMS Conference in Lett. 107 (2011) 193003. est known nuclei was predicted by Ottawa (AMS-14). Currently there are 13. P. Milota et al., Nucl Instr. Meth. B nuclear shell model theories. These more than 100 AMS facilities world- 266 (2008) 2279. nuclei were nicknamed SHEs (super- wide [1], utilizing long-lived radionu- 14. F. Quinto et al., Anal. Chem. 87 (2015) heavy elements). Since it was clear clides to study a multitude of fields in 5766. from the onset that this island cannot every domain of our environment at 15. A. Wallner et al., Nature Communica- be reached by heavy ion nuclear reac- large. Through its recent addition of tions 6 (2016) 5956. tions in the laboratory with available a laser–anion interaction (Figure 1), 16. G. Korschinek and W. Kutschera, projectiles and targets, many searches VERA will be able to substantially Nucl. Phys. A 944 (2015) 190. were performed to find minute traces increase the number of radionuclides of primordial SHE nuclides in na- available for AMS measurements ture. However, such nuclides would (Figure 2). This promises an exciting have to have half-lives of at least 100 future of AMS at VERA for the years million years in order to survive in to come. measureable quantities the 4.5 billion years since the solar system formed. Acknowledgments After reports of a positive evidence We gratefully acknowledge the col- for the existence of SHEs from mea- laboration with the many students and surements with inductively coupled colleagues from Vienna and abroad. plasma sector field mass spectrom- We particularly thank the colleagues Robin Golser etry (ICP-SF-MS) by a group from who worked with us during the past University of Vienna, Vienna, Austria the Hebrew University in Jerusalem, 20 years at VERA: Alfred Priller, Pe- two AMS labs set out to check these ter Steier, and Eva Maria Wild. claims. The AMS group at the Maier Leibniz Laboratory in Munich per- formed AMS experiments at their References 14-MV tandem accelerator and the 1. H.-A. Synal, Int. J. Mass Spectr. 349– VERA lab used the 3-MV tandem ac- 350 (2013) 192. celerator. A summary of these efforts 2. W. Kutschera, Int. J. Mass Spectr. is presented in Ref. [16] and Figure 349–350 (2013) 203. 4. These experiments did not find any 3. D. Berkovits et al., Nucl. Instr. Meth. A 281 (1989) 663. trace of SHEs with concentration lim- 4. Y. Liu et al., Appl. Phys. Lett. 87 its many orders of magnitude lower (2005) 113504. Walter Kutschera than the positive claims. They also in- 5. M. Martschini et al., Int. J. Mass University of Vienna, Vienna, Austria cluded searches for 42 additional SHE Spectr. 415 (2017) 9. nuclides covering part of the center of 6. E. M. Wild et al., Nature 435 (2005) the island of stability around mass 300 322. (Z = 114, N = 184). Again no evidence 7. W. Kutschera et al., Radiocarbon 54 for the existence of SHE nuclides was (2012) 407. found [16]. 8. K. L. Spalding et al., Cell, 122 (2005) 133.
34 Nuclear Physics News, Vol. 27, No. 3, 2017 meeting reports
The 26th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2017
The 26th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions, Quark Matter 2017, was held in Chicago, Illinois, USA on 5–11 February 2017. Quark Matter is the major conference series in the field of high-energy heavy-ion physics, ap- proaching a 40-year history. The first in this series took place in Darmstadt in 1980. Since then, the conferences have been organized approximately every 1.5 years. The three most recent meetings before Chicago were held in Kobe, Japan in September 2015; Darmstadt, Germany in May 2014; and Washington, D.C., USA in August 2012. The scientific topics covered at the meeting included both experimen- tal and theoretical QCD studies of nu- Figure 1. Electromagnetic probes; QCD in small systems; QCD at high temper- clear matter at high temperatures and/ ature; Chiral Figure 1. Jürgen Schukraft delivered a keynote talk “Status and or baryon densities, created in nuclear Key Open questions” in the opening session of Quark Matter 2017 conference. collisions at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven conference was opened with a day Astrophysics; Collective Dynamics; National Laboratory and the Large of plenary talks and a poster session; New Theoretical Developments; Cor- Hadron Collider at CERN. Over 700 the next two days were dedicated relations and Fluctuations; and Future participants (over half of them stu- to selected parallel talks; and the re- Experimental Facilities, Upgrades, dents and young scientists) gathered maining time was allocated to plenary and Instrumentation. in Chicago to present and discuss their presentations. Over 500 presentations The conference highlighted many work in talks and posters covering a were made at the meeting, including advances in theory and results from broad range of topics in the field. 38 invited plenary talks, 176 parallel experimental studies of heavy ion col- In the Quark Matter 2017 open- talks, and over 300 posters. Eight of lisions. PHENIX and STAR presented ing ceremony, conference participants the poster presentations were selected a harvest of new results from RHIC’s were greeted by Illinois Representa- by the conference Awards Commit- heavy flavor program, including first tive Raja Krishnamoorthi, Deputy tee for a flash talk presentation in the ever measurements of baryon to me- Mayor of the City of Chicago Steve last plenary session. Parallel sessions son ratios in the charm sector. The Koch, and the Associate Director for of the conference focused on topical RHIC experiments extended their sys- Nuclear Physics of the U.S. Depart- discussions; the list of parallel session tematic studies of collective flow in ment of Energy Dr. Timothy Hall- topics included Initial State Physics AuAu collisions to higher precision man. The keynote speaker of the ses- and Approach to Equilibrium; Jets and measurements in the charmed sector, sion was Dr. Jürgen Schukraft, who High-pT Hadrons; Electromagnetic and to detailed studies of asymmet- summarized the status of the field Probes; QCD in Small Systems; QCD ric collision systems. Hydrodynamic ahead of new results to be presented at High Temperature; Chiral Magnetic behavior of the quark-gluon plasma at the conference and posed several Effect, Vorticity and Spin Polariza- medium was tested meticulously by a important open questions yet to be tion; Quarkonia and Open Heavy Fla- suite of identified particle flow results answered. The main program of the vours; Baryon-Rich QCD Matter and from all three LHC experiments, in
Vol. 27, No. 3, 2017, Nuclear Physics News 35 meeting reports
both PbPb and pPb collisions. These dynamic evolution of the quark-gluon offering a set of introductory lectures new LHC measurements so far span medium to its tomography with the to students and young scientists. Fol- the first two generations of quark help of jet–medium interactions, and lowing this tradition, the organizers of flavors, but bottom hadron measure- from large to small systems. Tell- Quark Matter 2017 invited once more ments are now also within experimen- ingly, the complexity of the field has a team of expert speakers to discuss tal reach. Surprising new findings of recently led to an increased number of the foundations of the field, new ex- the evolution of the charge-separation collaborative efforts within the theory perimental methods, and recent theo- signal observed in azimuthal correla- community, following the long-stand- retical advances in deciphering the tions from AuAu collisions at RHIC ing tradition established on the experi- signals from quark gluon plasma. The to PbPb and pPb events at the LHC mental side: the BEST, THOR, JET, Student Day attendance at the Chi- generated a robust discussion whether and JETSCAPE Collaborations all cago meeting exceeded all previous the observations are indeed caused by presented results from and/or future records—about 400(!) participants the chiral magnetic effect as previ- plans for these joint efforts. registered for this special event. A ously argued for the RHIC data. The The conference was concluded contributing factor to this success is exploration of hard probes has seen an by an awards ceremony highlight- that Quark Matter conferences have explosion of novel methods and ob- ing achievements of a number of established the custom of providing servables advancing the understand- young scientists. Björn Schenke financial support for large numbers of ing of jet quenching phenomena: both of Brookhaven National Labora- students and young postdocs from all RHIC and LHC experimentalists pre- tory was presented with the 2017 nations to facilitate their attendance at sented results on jet mass, jet shape, Zimányi Medal in Nuclear Theory, this most important conference in the and splitting function measurements, for his pioneering work in modeling field. Generous contributions from a exploring jet–medium interactions in the dynamics of heavy ion collisions. large number of national and interna- ever finer detail. Zhoudunming Tu (Rice University) tional supporters made it possible this Theory highlights included im- and Azumi Sakai (Sophia University) time to provide travel support to more provements in the modeling of the won Nuclear Physics A Young Scien- than 300 young participants. early pre-equilibrium stage in heavy tist Awards for the best experimental Additional information about the ion collisions, as well as deeper ex- and theoretical talks, respectively, Quark Matter 2017 Conference, in- plorations of the profound impact of presented in the parallel sessions. At cluding program details and presenta- initial state fluctuations on the overall the end of the awards ceremony the tion materials as well as conference event dynamics and on probes that organizers of the 27th edition of the photos, is available on our homepage are used to study the quark-gluon me- conference unveiled details of Quark at http://qm2017.phy.uic.edu. dium at different scales. Very impres- Matter 2018: that meeting will be held sive advances made in the data-driven in Venice, Italy, on 13–19 May 2018. Russell Betts determination of QGP parameters Among the main objectives of the Illinois Institute of Technology, from global Bayesian analysis were Quark Matter conferences is fulfill- Chicago, Illinois, USA undoubtedly one of the highlights of ing an educational mission: to help the Chicago meeting. Overall, signifi- raise the next generation of scientists. Olga Evdokimov cant progress continues to be made Bringing world-renowned experimen- University of Illinois at Chicago, in the development of a comprehen- tal and theoretical physicists of the Chicago, Illinois, USA sive theoretical description and dy- field together with young postdocs namical modeling of the entire evo- and students to discuss the latest de- Ulrich Heinz lution of heavy ion collisions, from velopments and advances in the field Ohio State University, Columbus, the initial stage to the formation of a is only a part of this mission. In addi- Ohio, USA quark-gluon plasma and its eventual tion, the first day of the conference has hadronization, from the bulk (hydro) traditionally been entirely devoted to
36 Nuclear Physics News, Vol. 27, No. 3, 2017 meeting reports
Jefferson Lab Hosts Workshop on New Scientific Applications of its Low Energy Recirculator Facility
On 17 March 2017, Jefferson Lab, in Newport News, Virginia, hosted a workshop exploring potential uses of its Low Energy Recirculator Facility (LERF; Figure 1). The goal of this workshop was to inform researchers and educators of opportunities at the LERF facility, and to explore its re- search and educational potential. The LERF, which houses an energy recov- ery linac and seven user labs, provides excellent opportunities for funda- mental and applied science research as well as education and training. In addition to the 170 MeV, high-current, Figure 1. LERF workshop participants. recirculating accelerator, the facility possesses state-of-the-art equipment tial uses of the LERF for nuclear phys- and Materials Research. The equip- for pulsed laser deposition, micro- ics, isotope production, and positron ment available in the ODU labs at the machining, XHV vacuum work, laser- production. All of these applications lab was then described. The last talk generated TeraHertz with associated would use the facility accelerator. discussed possible laser applications instrumentation, and pulsed fiber laser The LERF complements CEBAF as that might be developed in the LERF. development. a nuclear physics accelerator by pro- They range from THz production, to The one day “Workshop on Sci- viding low energy beam at high cur- production of electron beams with an- ence at LERF” was organized into rent. With an internal target one can, gular momentum, to next-generation several topical sessions dealing with in principle, preserve the beam quality photocathode drive lasers. science using the LERF beam, and well enough after the target to allow At a Panel Discussion, new av- science possible with the LERF lab energy recovery. In addition to this, enues for research support were dis- equipment. A tour of the Old Domin- when operated as a single pass device cussed as well as some new potential ion University Area Research Center for isotope or positron production, the applications. One new application was (ODU ARC) and LERF labs was or- accelerator can provide over 100 kW the use of the facility Laser Micro- ganized for workshop participants, of beam power to a target. Since the Engineering Station to fabricate THz and a panel discussion concluded the beam is also very bright with a very waveguides. It was also pointed out workshop proceedings. The workshop small energy spread, it can be used as that there is a very strong need for scientific program and presentations an extremely bright source of low en- bright low energy positron sources are available at https://www.jlab.org/ ergy positrons. and it may be possible to sell time at a indico/event/199/. The workshop at- After a tour of the facility and the positron use facility. It was agreed to tracted 51 registered participants from ODU labs at Jefferson Lab, the talks put together a proposal for a Scientific Jefferson Lab, NASA, and nearby uni- concentrated on user experiments Users Workshop of low energy posi- versities, considerably exceeding ini- in the User Labs that did not neces- trons to make the science case for such tial expectations. sarily use the FEL. A representative a facility. After presentations describing how from Virginia Diodes described po- S. Benson outside projects are carried out at Jef- tential uses and applications of THz Jefferson LAB ferson Lab stressing the need for safety radiation, and two previous users of and careful resource management and the LERF facility gave summaries of G. Krafft a historical perspective of the facility, how they used the LERF User Labs to Jefferson LAB, ODU there were several talks about poten- carry out user programs in nanotubes
Vol. 27, No. 3, 2017, Nuclear Physics News 37 European Marine Board based in Ostend and are looking forward to a renewed remit for the MatSEEC committee on materials science. In addition, we hope that recent discussions will soon lead to new entities European news and research views through our networking, funding, and co-‐ordination activities, the ESF will continue to being set up by ESF, and to existing ones being hosted at the ESF Headquarters in Strasbourg. contribute strongly to the development uropean of the E R esearch A rea. Overall, we have a highly qualified international and interdisciplinary team with a deep understanding of ESF After ESF: The Launch of Science Connect science matters and research infrastructures across Europe. Through Science Connect, we are providing that experience, along with forward thinking and planning, to all our members, , partners, and customers both public and . private We are currently engaged in over a dozen key projects including participation as
Partner or Coordinator in the highly visible European Commission’s Graphene Flagship or in the inventory and web portal of European research infrastructures MERIL.
We are also expanding our resource network of research expertise and talent by establishing the
Figure 1. The ESF-Science Connect launch event in Strasbourg City Hall on 3 April 2017 was attended by senior figures
• Career tracking—where we generate high quality, reliable information on supply and demand for
doctorate holders and their overall availability and mobility in the European Research . Area
• Programme and Project Management and Administration—this alleviates the administrative
burden on research infrastructures and contributes to research success. Figure 2. The President and Chief Executive with Dr Gabriele-Elisabeth Körner, NuPECC Executive Scientific Secretary, and
Scientific effective Secretary, secretariats, and colleagues hosting and platforms, o rgani staff zational from structures, the and former strategic MatSEEC expert committee. advice. 38 Nuclear Physics News, Vol. 27, No. 3, 2017 Today hese t Expert Boards include NuPECC, and also the European Space Sciences Committee (ESSC) and the Committee on Radio Astronomy Frequencies (CRAF). We continue to lead joint projects with the news and views
strongly to the development of the Eu- Virtual Institutes—where we pro- ent by establishing the ESF Commu- ropean Research Area. vide effective secretariats, hosting nity of Experts. Our Community of We will do this by enabling and platforms, organizational struc- Experts reactivate the ESF network supporting the science community tures, and strategic advice. of international academics, science and science stakeholders with unique policy experts, key decision-makers, Today these Expert Boards include strengths, insights, and technical ca- and stakeholders across the European NuPECC, and also the European Space pabilities—partnering with custom- and global research landscape. We al- Sciences Committee (ESSC) and the ers in leading successful projects and ready have over 2,200 new members Committee on Radio Astronomy Fre- facilitating informed decision making on board, including our College of Re- quencies (CRAF). We continue to lead through evidence-based science and view Panel members and our College joint projects with the European Ma- through a wide range of support ser- of Research Associates. Find more rine Board based in Ostend and are vices. In brief, our functions cover five at: http://www.esf.org/community-of- looking forward to a renewed remit for key areas: experts/. the MatSEEC committee on materials We are now looking forward with ● Peer review—where we identify science. In addition, we hope that re- confidence, energy, and enthusiasm to the best research and optimize cent discussions will soon lead to new our continuous further contribution to the use of our partners’ internal entities being set up by ESF, and to science and science-related activities resources. existing ones being hosted at the ESF over Europe. ● Evaluation—where we work to Headquarters in Strasbourg. maximize the impact of policies Overall, we have a highly quali- ORCID and programs to facilitate the fied international and interdisciplinary Jean-Claude Worms achievement of research excel- team with a deep understanding of sci- http://orcid.org/0000-0002-0851-7341 lence. ence matters and research infrastruc- ● Career tracking—where we gen- tures across Europe. Through Science erate high quality, reliable infor- Connect, we are providing that experi- mation on supply and demand ence, along with forward thinking and for doctorate holders and their planning, to all our members, part- overall availability and mobility ners, and customers, both public and in the European Research Area. private. We are currently engaged in ● Programme and Project Manage- over a dozen key projects including ment and Administration—this participation as Partner or Coordinator alleviates the administrative bur- in the highly visible European Com- den on research infrastructures mission’s Graphene Flagship or in the and contributes to research suc- inventory and web portal of European Jean-Claude Worms cess. research infrastructures MERIL. ESF Chief Executive ● Host for several internationally We are also expanding our resource recognized Expert Boards and network of research expertise and tal-
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Vol. 27, No. 3, 2017, Nuclear Physics News 39 news and views
An Important Milestone: Groundbreaking Ceremony for the FAIR Accelerator Facility
Figure 1. Groundbreaking ceremony for the FAIR facility.
The construction of the interna- circumference of 1,100 meters. Con- At the ceremony, government of- tional accelerator facility FAIR (Facil- nected to it is a complex system of ficials and scientists from Germany ity for Antiproton and Ion Research) storage rings and experimental sta- and abroad extended greetings and has begun. The start of building con- tions. Scientists will be able to study symbolically broke the ground with struction and civil engineering work is the universe in the lab: FAIR will ad- a shovel. This crucial milestone was a crucial moment for one of the largest dress fundamental problems such as attended by representatives from all construction projects for scientific re- the origin of heavy elements in the nine partner countries. search worldwide. On 4 July 2017, the universe or the structure of neutron In line with the groundbreaking groundbreaking ceremony (Figure 1) stars, but also applications from ma- ceremony, FAIR also began FAIR was held for the large ring accelerator terial sciences to medicine. Phase 0 of its experimentation pro- SIS 100, which will be the key compo- Over the past few weeks and gram in order to harmonize research nent of the future accelerator facility months, extensive preparations have operations with the progress of con- FAIR. The construction site is located been made for the huge construction struction. Beam times are already be- to the northeast of GSI Helmholtz- project. For example, work is already ing scheduled for researchers at exist- zentrum für Schwerionenforschung in under way to connect the existing ac- ing GSI facilities and at components Darmstadt. celerator facilities of the GSI Helm- for FAIR. To conduct this research, FAIR will be a unique particle ac- holtzzentrum to the new FAIR com- scientists are using the GSI accelera- celerator facility with an investment plex. Retaining walls are being built tor facilities, which have been sub- volume of more than €1 billion. The and contracts have been awarded for stantially enhanced for their later use facility is being constructed by nine the excavation and installation of the as preaccelerators for FAIR and will partner countries and is scheduled ring tunnel following a successful call have their technology further up- to go into full operation in 2025. for bids. These were important prepa- graded in the future. Moreover, parts Around 3,000 scientists from all over ratory steps for the large-scale work of FAIR can already be used, includ- the world will work at FAIR, where on the FAIR infrastructure, which has ing the CRYRING storage ring. they will gain groundbreaking in- now begun with the groundbreaking sights into the structure of matter and ceremony for the SIS 100 ring acceler- Ingo Peter the development of the universe. The ator. The cutting-edge accelerator and GSI Darmstadt key component of FAIR will be an experiment facilities will be installed underground ring accelerator with a after the new buildings are completed.
40 Nuclear Physics News, Vol. 27, No. 3, 2017 calendar
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