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CERN get their grand OPERA

The 2000 tonne OPERA (Oscillation interaction point. Recognizing these Project with Emulsion Tracking tiny decay kinks is the main goal of Apparatus) experiment has been the OPERA experiment. approved for construction and To do so it must use a detector operation in the CERN with excellent spatial resolution Beam to Gran Sasso project.The over its whole 2000 tonne mass. experiment involves 33 research The technique chosen is that of the institutes in 12 countries, including Emulsion Cloud Chamber (ECC), CERN, China and Japan. with sheets of passive absorber The CERN Neutrino Beam to Gran (lead) material interspersed with Sasso project, now under construc­ emulsion layers to reveal the tracks tion (December 2000 p7), will send left by neutrino interactions.The a beam of high-energy neutrinos Fig. 1. OPERA uses cells of 1 mm thick passive lead plates basic OPERA unit is a cell made of from CERN to the Italian under­ interspersed by thin films, made of a pair of about 50 Jim a 1 mm thick lead plate followed ground Gran Sasso laboratory, a emulsion layers on either side of a 200 \im plastic base. by a thin film, made of a pair of distance of 730 km, where the This shows how neutrino tracks would begin. 50 |jm emulsion layers on either OPERA detector will be assembled. side of a 200 pm plastic base The first neutrinos are expected to (figure 1). Cells will be arranged in be sent in 2005. turn in removable "bricks", and the Classically, neutrinos come in bricks used to build "walls", three varieties - , and modules and supermodules. , depending on their partner Downstream of the ECC lattice will .These neutrino varieties be a muon spectrometer. are supposed to be immutable, so Each removable brick, weighing that a neutrino born alongside a 8.3 kg, will have dimensions of muon should remain a muon 10.2 12.7 cm transverse to the neutrino for ever. beam and 7.5 cm along the beam, However, major experiments and will be made up of 56 individual monitoring the arrival of neutrinos cells. A wall will be built of 3264 produced in the atmosphere by bricks and, with two planes of elec­ cosmic rays provide strong indi­ Simulation of a interaction in OPERA. The beam tronic trackers (plastic cations that neutrinos are not comes in from the left and hits a nucleus in a wall of target read out by wavelength-shifting immutable (October 2000 p31).To bricks. Each wall is followed by target tracker planes fibres), will make up a module. explain this observed behaviour, perpendicular to the beam. The long track escaping on the Each target supermodule will some neutrinos that start off muon- right is a muon. consist of 24 modules, and the like could transform en route into whole detector, with a cross-section tau-like neutrinos. of about 6 x 7 m perpendicular to To maximize the chances of see­ the beam, will contain three super- ing such neutrino "oscillations", the modules, representing a total of experiment needs a long "base­ 235000 bricks. line", in this case the 730 km The effectiveness of the ECC between CERN and the Gran Sasso technique was shown last year laboratory. Because of these oscil­ through its use in the first obser­ lations, a neutrino beam starting off vation of explicit tau-neutrino muon-like as it left CERN would signals by the DONUT (Direct contain tau-neutrinos on arrival at Observation of the NUTau) experi­ Gran Sasso. When they interact, ment at (September 2000 these tau-neutrinos can produce p6). DONUT monitored the neutrino highly unstable tau , which outcome after slamming a high- decay within 1 mm of the neutrino Schematic view of the full OPERA detector. energy beam into a compact

4 CERN Courier June 2001 NEWS

"beam dump", thus generating a small num­ ber of tau-like neutrinos directly, rather than through oscillations. Because of its natural divergence, by the Three new experiments set to time the neutrino beam reaches Gran Sasso it will have spread out across an area of about arrive at SLAC's End Station A 800 m.This means that OPERA, mighty as it is, will only see a small slice of the arriving beam. End Station A, the venerable fixed-target To build the detector, an assembly line at facility at the end of the two mile electron Gran Sasso will stack lead plates and linear accelerator beam at SLAC, Stanford, emulsion films into- bricks at the rate of about where were discovered in 1967, will two per minute. Computer-controlled robots soon see a high-energy beam of polarized will arrange the bricks in their allocated posi­ (-oriented) as three newly tions. It will take about a year to fill the approved experiments move onto the floor. detector with bricks. An international collaboration led by Peter Emulsion films have a long history in Bosted and Stephen Rock (Massachusetts), experiments, one milestone Donald Crabb (Virginia) and Keith Griffioen having been the discovery of the in (William and Mary) will use paper-thin 1947 cosmic-ray studies. Automatic diamond wafers to generate coherent emulsion scanning by computerized micro­ beams with energies of up to 48 GeV. A set of new experiments at End Station A at scopes was pioneered by the Nagoya group, Louis Osborne and Roy Schwitters pion­ SLAC, Stanford, will use thin diamond starting in the late 1970s. Japanese emul­ eered this technique at SLAC in 1970, when wafers to generate coherent photon beams sions were used for the CHORUS neutrino the maximum electron energy was 20 GeV. with energies of up to 48 GeV from the SLAC experiment at CERN and for DONUT at Specific crystal planes of the diamond are electron beams. The 8x8 mm diamond Fermilab. However, OPERA will need a much precisely aligned with the electron beam to target is 1 mm thick. greater amount of emulsion than any of its create a diffraction grating for the predecessors, and new industrial techniques bremsstrahlung photons produced by elec­ E160 will measure the dependence of are being perfected in a collaboration trons interacting in the crystal.This process J/psi production on nuclear composition by between Nagoya and Fuji Film. yields distinct spikes in the photon energy firing unpolarized photons at several different While the experiment is running, the spectrum. Small-angle collimation then unpolarized nuclear targets. This experiment complete detector will be continuously moni­ enhances the ratio of coherent to incoherent will aid searches for the - plasma tored by its own electronic detectors.These radiation. SLAC's highly polarized electron at CERN's SPS (Super Proton Synchrotron) electronic trackers, located downstream of beam, with energies now as high as 50 GeV, and Brookhaven's RHIC (Relativistic Heavy each wall, will also be used to identify the will be used to generate more than a billion Ion Collider), in which one expected signature brick where a neutrino interaction occurs. circularly polarized photons per second. is the suppression of J/psi production. A These bricks (about 30 per day) will be The three new experiments are known as better understanding of the simpler photo- removed outside the underground hall for E159, E160 and E161. E161 will study the production process should help to interpret calibration.They will then be taken apart and contribution of to the spin of nucléons. those results. the emulsion plates developed. Since the 1980s, - scattering E159 will test the Gerasimov-Drell-Hearn Faster scanning procedures than those experiments at CERN, SLAC and DESY have sum rule using polarized photons and polar­

used for the CHORUS and DONUT experi­ established that the constituent quarks are ized ammonia and ND3 targets. In this sum ments will be needed to locate the neutrino responsible for only 25 per cent of the rule, the difference between the total cross- interactions.These are now being developed. nucleon's spin.The rest must come from the sections with the photon spin-polarized Further scanning will search for a tell-tale orbital motion of quarks and gluons and from parallel versus antiparallel to the nucléon spin millimetre track followed by a kink, the the intrinsic spin of the gluons. is related to the anomalous magnetic moment characteristic fingerprint of a tau decay and E161 will study gluon contributions to of the nucléon. If this prediction is not verified, therefore of a tau-neutrino interaction. nucléon spin via a photon-gluon fusion it could suggest possible excitations of the At the rate suggested by process, in which a circularly polarized photon nucléon not previously identified - or even experiments to date, OPERA should see about merges with a polarized gluon to form an new particles or interactions not 15 tau-neutrino interactions in five years of unbound charm-anticharm quark pair.The encompassed by the . running with the nominal performance of the production of charm quarks is established via At the heart of all three experiments lie neutrino beam from CERN to Gran Sasso. If their decay to , which will be identified diamonds and charm. Once beautifully set to so, it will have proved that the disappearance using a long dipole magnet filled with show their best facets to the electron beam, of muon-like neutrinos observed in atmos­ alumina. Polarized LiD will be used as the these diamonds will indeed become a pheric neutrino experiments is indeed due to target, cooled to 300 mK with a dilution refrig­ physicist's best friend. oscillations into tau-like neutrinos. erator inherited from CERN. Peter Bosted, University of Massachusetts.

CERN Courier June 2001 5 NEWS

CONFERENCE High-energy accelerators look to R&D

The rhythm of the International High Energy Alexander Skrinsky of Novosibirsk thought Accelerator Conference (HEACC), held once that a normal conducting S-band (3 GHz) every three years, is well matched to the route was the way to go for a "frontier" gradual evolution of the accelerator scene. machine, despite the 60 MV/m threats. The latest venue, in Tsukuba, Japan, in March, Fresh from the recent launch of the super- reflected the continued emergence of colli­ conductingTESLA idea at DESY (May p6), ders as the preferred experimental tool, both laboratory director Albrecht Wagner described at high energy and for special physics areas, how 500 GeV collision energy was already on and the change in emphasis on high-energy the cards with the achieved 23.4 MV/m fixed target experiments. A small, select meet­ accelerating fields, but that 800 GeV was ing, HEACC provides a sharp overview of the attainable if performance could be guaran­ current scene, contrasting with the blurred, teed at 35 MV/m, and even beyond with subjective picture that can emerge from large careful electropolishing. meetings with many parallel sessions. The clamping ring at the Accelerator Test LHC project director Lyn Evans of CERN In his introductory HEACC talk, Hirotaka Facility (ATF) at the Japanese KEK laboratory pointed out the sterling work already achieved Sugawara, director of the host KEK laboratory, has attained promising beam emittances by the PS synchrotron at CERN, which will be stressed that the real physics objectives are for (size x divergence) for new electron- the LHC pre-injector.This beam-preparation a 100TeV proton collider and a lOTeV elec­ linear colliders. baton now passes to the next link in the LHC tron-positron collider, for which current projects injector chain, the SPS.The LHC commission­ are only precursors. His call for more accelerator machines, and, at many major laboratories, ing schedule foresees a sector test in 2004, R&D effort was echoed throughout the meeting. vigorous research and development work is the complete ring cooled to 2 K in 2005 and For high-energy electron-positron colliders, looking at the problems to be solved en route commissioning in 2006. the machines at SLAC, Stanford, and LER to higher energies. New ring on the block is Brookhaven's RHIC CERN, have ceased operation since the previ­ At the AcceleratorTest Facility (ATF) at KEK, heavy-ion collider, which was commissioned ous HEACC at Dubna in 1998, and the Japan, the emittance (size x divergence) of a last year (October 2000 p5) and has already emphasis has turned instead to lower-energy beam has reached 10"11 rad m - a promising produced initial physics. Derek Lowenstein colliders - PEP-II at SLAC and KEKB, Japan, figure for linear colliders. Less constructive at pointed out that ion-collision energy will soon using unequal electron and positron energies first glance is the breakdown effects encoun­ be boosted to the 200 GeV per nucléon to probe the physics of B particles, containing tered at 60 MV/m in non-superconducting design figure. Polarized will be the fifth ("b") quark.These colliders have accelerating cavities at ATF, at the counterpart accelerated using a Siberian Snake magnet quickly broken all records for luminosity (colli­ facility at SLAC (for the "Next Linear Collider") structure. Another new RHIC plan is a 52 MeV sion rate), exceeding 1033/cm2/s. and elsewhere. electron linac for cooling the heavy-ion beam Having made major contributions to B However, not all delegates were that to increase collision (luminosity) performance physics for many years, the CESR pessimistic: Greg Loew of SLAC dismissed this (52 MeV is the electron mass scale for RHIC's electron-positron collider at Cornell is now obstacle as "a bump in the road", while Ron 100 GeV per nucléon beams). looking to reduce its operating energy to inves­ Ruth of SLAC proposed new cavity configura­ Fermilab'sTevatron proton- collider tigate other quark sectors. Another special tions exploiting standing waves. has just begun its new run, and luminosities research focus is the tau-charm sector, where On both sides of the Pacific, R&D pushes should eventually attain 5 x 1032/cm2/s. the Budker Institute at Novosibirsk, long-time ahead towards an X-band (11.4 GHz) scheme Electron cooling should soon be introduced for an electron-positron collider stronghold, con­ using high-power klystrons based on periodic the antiproton collector ring (May p7). tinues to develop plans. permanent magnet focusing, yielding 70 MW For the long-term future, there was talk of In its build-up, LEP was frequently referred and a few microseconds in pulse length. LHC II at CERN, with new magnets operating at to as the last of the big electron-positron rings. CERN has its own plan for a linear almost double the current field, while Fermilab However, with talk of a possible Very Large electron-positron collider - the CLIC scheme is looking at various VLHC options to attain Collider (VLHC), the ring of which - using a drive beam instead of conventional collision energies of some 40TeV, compared would dwarf CERN's 27 km LHC project, the klystrons.The CTF2 CLIC test facility at CERN with the LHC's 16TeV. VLHC circumferences ultimate circular electron-positron machine uses transfer structures yielding 100 MW of range from 100 to 500 km, depending on the could be built in such a tunnel, attaining colli­ 30 GHz power to study how the main linac strength of the bending magnets used. sion energies of around 370 GeV. could withstand accelerating fields of more Although not strictly a hadron collider, However, the preferred route to high-energy than 60 MV/m. A major design report is DESY's HERA electron-proton machine has a electron-positron colliders is now via linear expected in 2005. In his summary talk, field of physics all to itself and is seeking to

6 CERN Courier June 2001 NEWS Cryogenic XRay We're an boost collision rates by squeezing the collid­ Diffraction Open Book ing beams more tightly together (May p5). The relatively new idea of using muon rings as intense neutrino sources has already resulted in several proposals (April 2000 pl7), which were summarized by Alessandra Lombardi of CERN. The energies of the envis­ aged proton driver machines range from 2.2 GeV at CERN to 15 GeV at Fermilab, 24 GeV at Brookhaven and 50 GeV in Japan, using different approaches.The CERN scheme foresees a superconducting proton linac, which could also be used as a new injector for the synchrotron chain. Work in Japan is helped by the recently approved KEK/JAERI proton scheme (March p8). However, worldwide enthusiasm for the new idea is being hampered at the moment by inadequate resources. Displex With National Instruments, R&D for new accelerator methods appears you define your measurement to have reached something of a plateau, Helitran and automation solution. where conventional ideas have run out of •1.7to800K • Networked measurement steam and where there are few new and automation solutions contenders to take their place. Continually •Closed and open increasing laser power is one pointer, cycle cryostat • Machine vision and however, and Konstantin Lotov of Novosibirsk goniometer interfaces motion control underlined that the high accelerating fields •Huber 512,5020 • PXr/CompactPCr available over plasma dimensions need to be instrumentation extended over longer distances. •Bruker D8, D5000 £ • LabVIEW™ graphical In his concluding talk, CERN accelerator •Newport KAPPA programming director Kurt Hubner proudly pointed to the o accelerator physicists'track record of "deliv­ •Rigaku, Scintag, 0 • Tools for text-based programming ering rather than promising". He stressed Philips • that all hardware should be "tested, tested, • GPIB instrument control tested" to avoid disappointment and to exploit success, and recommended that new projects should request adequate resources from the start, and not feel apologetic about Call for your FREE it. With notable accomplishments already Measurement and having been achieved by international Automation Catalog2001 collaborations, it is important to continue this tradition, said Hubner. ! TheTsukuba HEACC was organized by Koji Takata of the KEK laboratory. Many HEACC (0 *T NATIONAL delegates will reassemble in Chicago in June ^INSTRUMENTS for the US Particle Accelerator Conference. Advanced Research Conscious that the accelerator conference agenda is possibly overloaded, there was Systems, Inc. discussion of how this could be reduced, and [email protected] 905 Harrison Street #109 National Instruments Switzerland a committee headed by Ferdinand Willeke of Sonnenbergstr. 53 DESY ("we cannot do enough work to fill the Allentown, PA 18103 CH-5408 Ennetbaden 610 439 8022 Fax. 056/200 51 55 available speaking time") will make recom­ [email protected] Fax 610 439 1184 ni.com/switzerland mendations. However, HEACC in some form or e mail; [email protected] Deutschland 089/741 31 30 another will surely continue to appear on the Visit our website @ Osterreich 0662/45 79 900 high-energy accelerator agenda. Copyright © 2001 National Information from Karlheinz Schindl, CERN. www.arsciyo.com

CERN Courier June 2001 7 1 CREATIVE ÉK CTBOfHC SYSTEMS is 20 wears old... m We enjoyed the days of NI M and CAM AC W We survived the days of FASTBUS CES CREATIVE ELECTRONIC SYSTEMS 3S aveulie Eugène-Lance We went for it with VME (3M212 Grancf-Lancy, Switzerland internet http://www.ces.ch We refused to adapt CPCI to physics time OS from PSOS, VBTX, 0$~9, VxWorks, Lynx ill CES Switzerland VMS and bypassed Windows to support LINUX lBk*4î22M43iM ¥mc+4iM394J4M Emaifc ce$@ce$xti Our SYSTEMS AND TECHNOLOGY IS DEPLOYED IN WORJDHTEADING TELECOM PROGRAMS, CES Germany AS WELL AS LEADING EUROPEAN AEROSPACE PROGRAMS. Tel:+49.60.51.96J7.41 Fax:+49.60.51.96.9738 - BUT - ft Email: norheit Joerch@cesxli MEMBER OUR ROOTS IN PHYSICS AND WILL ALWAYS TRY TO OFFER YOU COMPLETE • HARDWARE AND SOFTWARE SOLUTIONS IN THE FIELD OF INTELLIGENT INTERFACES, CES USA COMP„«„B CORES A„< NETWORFC ACCESS. Te!:+!51SJ43J445 FaPC+î 510.843J447 Email: [email protected] Your Ltb learn I

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