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Suppression of charged particle production at large transverse momentum in central Pb–Pb collisions at √sNN = 2.76 TeV

Inclusive transverse momentum spectra of primary charged particles in Pb–Pb collisions at √sNN = 2.76 TeV have been measured by the ALICE Collaboration at the LHC. The data are presented for central and peripheral collisions, corresponding to 0–5% and 70–80% of the hadronic Pb–Pb cross section. The measured charged particle spectra in |η| < 0.8 and 0.3 < pT < 20 GeV/c are compared to the expectation in pp collisions at the same √sNN, scaled by the number of underlying nucleon–nucleon collisions. The comparison is expressed in terms of the nuclear modification factor RAA. The result indicates only weak medium effects (RAA ≈ 0.7) in peripheral collisions. In central collisions, RAA reaches a minimum of about 0.14 at pT = 6–7 GeV/c and increases significantly at larger pT . The measured suppression of high-pT particles is stronger than that observed at lower collision energies, indicating that a very dense medium is formed in central Pb–Pb collisions at the LHC.

nuclear modification factor; PbPb; 2.76 TeV; ALICE LHC

The ALICE Collaboration