Bochum 2009 – scientific programme
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HK: Fachverband Hadronen und Kerne
HK 33: Heavy Ion Collisions and QCD phases
HK 33.8: Talk
Tuesday, March 17, 2009, 18:45–19:00, H-ZO 10
Perspectives for the measurement of the χc radiative decay in the ALICE experiment at the LHC — •Ana Marin1, Pedro Gonzalez2, Pedro Ladron de Guevara2, Ernesto Lopez Torres3, and Eulogio Serradilla2 — 1GSI, Darmstadt (Germany) — 2CIEMAT, Madrid (Spain) — 3CEADEN, Ciudad Habana (Cuba)
Heavy quarkonia are considered as very promising probes for the deconfinement of the hot and dense matter formed in relativistic heavy-ion collisions. J/ψ suppression in central heavy-ion collisions beyond expectations from a pure nuclear absorption scenario has been observed at CERN SPS and RHIC energies. Measuring the fraction of J/ψ resulting from χc and ψ′ decays in pp and in heavy-ion collisions would help further understanding the mechanism for the suppression.
The LHC will provide pp (PbPb) collisions up to √s= 14 TeV (√sNN= 5.5 TeV). The three experiments (ATLAS, CMS and ALICE) have a large program devoted to quarkonia measurements (J/Ψ, Ψ′, Υ). Moreover, Monte Carlo studies demonstrate that, with the ALICE detector, it should be possible to reconstruct and separate the χc1 and χc2 in the radiative channel J/Ψ+γ, as two separated peaks. The low momentum photon from the decay is measured by reconstructing in the central barrel the e+e− pairs from photons converted mainly in the ITS material. The overall efficiency expected for χc reconstruction is about 0.9%. For pp collisions, the rate of observable χc’s is expected to be 1.2×10−3 per second, assuming a luminosity of 1030 cm−2s−1 and a perfect trigger. An overview of the reconstruction method as well as expected results in pp collisions at LHC will be presented.