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Un nouvel outil pour sonder le plasma de quarks et de gluons au LHC : EMCal, un calorimètre électromagnétique pour l'expérience ALICE. – EMCal

Submission summary

The EMCal project concerns a large electromagnetic calorimeter for the ALICE experiment at the LHC collider. The scientific goal is to provide for ALICE the best conditions for characterizing the photon and jet production at high transverse momentum and hence, upstream, for the physics of hard processes whose interest appeared as major at the RHIC collider energies in the studies related to the quark-gluon plasma search. With energies thirty times higher than at RHIC, the LHC will open a novel area in the domain of hard physics and that would have been detrimental that heavy ion physicists continue without such a possible investigation. If ATLAS and CMS are indeed equipped with well-suited detectors for measuring particles at high energies, ALICE has the specificity to have been designed for the quark-gluon plasma, thus for a heavy ion environment, hence offering specific research topics for ALICE, complementary to the other LHC experiments. Its time projection chamber will allow an identification of charged particles on a large domain in transverse momentum and rapidity. However, concerning the photon detection, ALICE is equipped with the PHOS photon spectrometer, very efficient but with an acceptance which is too small to perform hard physics studies in good conditions. This is to offset this inconvenient that the EMCal project is proposed. A collaboration of American, Italian and French physicists has been initiated in the fall of 2005 in order to start the EMCal project, with the common goal, the construction of this new modular detector from 2008 to 2010. Its installation in ALICE will do such that the number of detectors will be maximize for 2010 since it corresponds to the heavy ion mode at full luminosity. EMCal is composed by 10 SuperModules (SM) and by 2 half SuperModules (a total equivalent to 11 SuperModules). A standard SuperModule is an assembly of 24 StripModules (24 strips), each being formed by 12 modules. The calorimeter, fixed on its support structure, will be inserted in the L3 magnet of ALICE with a range of 110° in azimuth angle and a pseudo-rapidity between –0.7 and +0.7 around the time projection chamber. The technology which has been chosen is the so-called Shashlik calorimeter technology (already used by RD-36, PHENIX, STAR and LHCb experiments), alternating led and scintillator layers and collecting the light longitudinally via WLS optic fibers. The collected light is then converted with APD and transmitted to electronics cards adapted from the ones developed for PHOS. The choice of the Shashlik technology, the fact that a certain number of instrumental developments realized for PHOS can be adapted for EMCal, imply that the project do not present technological risks, as it has been confirmed through the risks analysis performed both by the American physicists and the IN2P3 review. From the national point of view, the participation to the EMCal project offers the opportunity to IN2P3, via the implication of 3 of its laboratories, Subatech–Nantes, LPSC–Grenoble and IPHC–Strasbourg, to significantly contribute to this new domain of physics. Initiators of the EMCal international collaboration, the participation of the French physicists and engineers is motivated by several reasons : to transfer their know-how and knowledge from their passed experiments (at RHIC and JLAB) to the LHC experiment, both for the physics analyses but also for the instrumental developments (conception and realization). The planning of EMCal being tightened, the management board has decided a task sharing according to the competences developed in each laboratory : Subatech will provide its expertise in mechanics and instrumentation, LPSC to the trigger and instrumentation, IPHC to the slow control. After examining the technical service possibilities in the three laboratories, we also propose to assemble and tests 288 modules at Subatech. Thanks to the infrastructure at LPSC, these modules will be assembled in SuperModules before being installed in ALICE at CERN. Six other SuperModules will be assembled at LPSC with the modules coming from American and Italian laboratories. The remaining SuperModules are made in the United States. Presently, some activities on the conception (mechanics, electronics cards) are done in the laboratories. Software developments for the data processing and data analysis are currently pursued under the responsibilities of IPHC. The EMCal project has been presented to the three laboratories management : the manpower has been identified and recognized as free for this project from 2008 to 2010.

Project coordination

Christelle ROY (Organisme de recherche)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

Help of the ANR 550,000 euros
Beginning and duration of the scientific project: - 36 Months

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