Abstract
Charmonia with different transverse momentum pT usually comes from different mechanisms in the relativistic heavy ion collisions. This work tries to review the theoretical studies on quarkonium evolutions in the deconfined medium produced in p-Pb and Pb-Pb collisions. The charmonia with high pT are mainly from the initial hadronic collisions, and therefore sensitive to the initial energy density of the bulk medium. For those charmonia within 0.1 < pT < 5 GeV/c at the energies of Large Hadron Collisions (LHC), They are mainly produced by the recombination of charm and anti-charm quarks in the medium. In the extremely low pT ∼ 1/RA (RA is the nuclear radius), additional contribution from the coherent interactions between electromagnetic fields generated by one nucleus and the target nucleus plays a non-negligible role in the J/ψ production even in semi-central Pb-Pb collisions.
Highlights
Since charmonium abnormal suppression proposed as one of the signals of the deconfined medium produced in nucleus-nucleus (AA) collisions [1], abundant theoretical studies [2,3,4,5,6,7,8] about charmonium evolutions in hot medium have been done to reveal different aspects of heavy quark (HQ) interactions with the bulk medium
As the heavy quark interactions at large distance are screened at first, charmonium states (J/ψ, χc, ψ(2S )) with different geometry sizes are sequentially melt as the medium temperature increases [10]
Nuclear modification factor RAA, defined as the ratio of charmonium yield in nucleus-nucleus (AA) collisions NAJ/Aψ and the production in proton-proton collisions scaled by the number of binary collisions NcollNpJ/pψ, measures the magnitude of hot medium effects on charmonia
Summary
Since charmonium abnormal suppression proposed as one of the signals of the deconfined medium produced in nucleus-nucleus (AA) collisions [1], abundant theoretical studies [2,3,4,5,6,7,8] about charmonium evolutions in hot medium have been done to reveal different aspects of heavy quark (HQ) interactions with the bulk medium. This enhancement is only located in the small transverse momentum region This phenomina is well clarified by the regeneration mechanism [15], where single charm and anti-charm quark from different pairs can combine into a new charmonium during the QGP expansion, due to the large binding energy of J/ψ in the thermal medium. EN2 − m2N/EN > 0.999c at RHIC and the LHC energies with the relation strong electromagnetic (EM) pulse from the moving protons can change charged/chiral particle evolutions such as Chiral Magnetic Effect (CME) [21], etc, and interact with the target nucleus to generate new particles called photoproduction [12, 22] This has been widely studied in Ultra-peripheral collisions absent of hadronic collisions, and are expected to be negligible with the existence of QGP.
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