Vorschau

PDF, Englisch - Hauptdokument Download (15MB) | Nutzungsbedingungen

Abstract

The measurement of J/ψ production in heavy-ion collisions is seen as a key measurement in the hunt for the Quark-Gluon Plasma. At high collision energies as reached at the LHC it was predicted that a significant fraction of the J/ψ yield is formed by (re)combination of deconfined charm and anticharm quarks in the medium or at the phase boundary. This mechanism is expected to be most important at very low transverse momentum. In this thesis the production of J/ψ mesons is studied at mid-rapidity (|y| < 0.9) in pp and Pb–Pb collisions at a collision energy of √s_NN = 5.02 TeV with ALICE. The J/ψ mesons are reconstructed in the e+e− decay channel down to vanishing transverse momentum (pT = 0). The electrons and positrons are identified using the specific energy loss dE/dx in the TPC. The J/ψ spectrum and the nuclear modification factor R_AA in most central collisions are consistent with models which include (re)combination as a dominant source of J/ψ production. The measurement of the first two moments of the pT distribution as a function of centrality shows that this mechanism becomes more important for more central collisions.