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HK: Fachverband Physik der Hadronen und Kerne

HK 39: Heavy Ion Collisions and QCD Phases VI

HK 39.1: Group Report

Wednesday, February 28, 2018, 16:30–17:00, HZO 60

J/ψ production in pp and Pb-Pb collisions at mid-rapidity with ALICE — •Raul Tonatiuh Jimenez Bustamante for the ALICE collaboration — GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany — Physikalisches Institut, University of Heidelberg, Heidelberg, Germany

Charmonium production is a key observable in pp and Pb-Pb collisions. The charmonium study in pp collisions can help to understand both fundamental QCD processes and hadronization mechanisms. J/ψ measurements as a function of multiplicity can help to explore the soft regime.

In the study of charmonium in Pb-Pb collisions several QGP effects have been observed, such as the suppression of charmonium states due to color screening. However, an enhancement due to (re)combination of uncorrelated charm and anti-charm quarks has been observed at LHC energies. This enhancement is more pronounced at low transverse momentum (p_T < 4.0 GeV/c).

ALICE provides unique capabilities among the LHC experiments to measure J/ψ production in the mid-rapidity (|y|<0.9) region down to p_T =0. In this talk, ALICE measurements in pp at √s = 13 TeV as a function of charged particle multiplicity will be shown. In addition, the inclusive J/ψ nuclear modification factor (R_AA) as a function of centrality and transverse momentum will be discussed and compared to model predictions.