Abstract
The inclusive J/ψ meson production in Pb–Pb collisions at a center-of-mass energy per nucleon–nucleon collision of sNN=5.02 TeV at midrapidity (|y|<0.9) is reported by the ALICE Collaboration. The measurements are performed in the dielectron decay channel, as a function of event centrality and J/ψ transverse momentum pT, down to pT=0. The J/ψ mean transverse momentum 〈pT〉 and rAA ratio, defined as 〈pT2〉PbPb/〈pT2〉pp, are evaluated. Both observables show a centrality dependence decreasing towards central (head-on) collisions. The J/ψ nuclear modification factor RAA exhibits a strong pT dependence with a large suppression at high pT and an increase to unity for decreasing pT. When integrating over the measured momentum range pT<10GeV/c, the J/ψRAA shows a weak centrality dependence. Each measurement is compared with results at lower center-of-mass energies and with ALICE measurements at forward rapidity, as well as to theory calculations. All reported features of the J/ψ production at low pT are consistent with a dominant contribution to the J/ψ yield originating from charm quark (re)combination.
Highlights
The Quark-Gluon Plasma (QGP) is a state of strongly-interacting matter characterized by quark and gluon degrees of freedom predicted by Quantum Chromodynamics (QCD) to exist at high temperature and energy density [1,2]
The experimental results are compared with different phenomenological models of the charmonium production in relativistic heavy-ion collisions, i.e. the statistical hadronization model (SHM) by Andronic et al [21], the comover interaction model (CIM) by Ferreiro [23,50] and two different microscopic transport models, by Zhao et al (TM1) [24] and by Zhou et al(TM2) [25]
In the SHM, all heavy quarks are produced during the initial hard partonic interactions followed by their thermalization in the QGP and the subsequent formation of bound states at the phase boundary according to their thermal weights
Summary
The Quark-Gluon Plasma (QGP) is a state of strongly-interacting matter characterized by quark and gluon degrees of freedom predicted by Quantum Chromodynamics (QCD) to exist at high temperature and energy density [1,2]. Such conditions are realized during the initial hot and dense stages of ultra-relativistic heavyion collisions. The J/ψ yield is expected to be suppressed compared to probes unaffected by the hot and dense medium or from expectations of the incoherent superposition of nucleon–nucleon collisions at the same energy. This was experimentally observed in the most central heavy-ion collisions at SPS [8,9,10] and RHIC [11,12,13] energies
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