Temperature-Dependent Meson-Charmonium Dissociation Reactions In Hadronic Matter

The lattice QCD predicts that the quark-gluon plasma?QGP?will be produced under the condition of high temperature and high density.With the temperature decreasing as the QGP evolves,QGP will phase into the hadronic matter.Using Relativistic Heavy Ion Collider?RHIC?at Brookhaven National Laboratory?BNL?and Large Hadron Collider?LHC?at European Organization for Nuclear Research?CERN?,researchers can obtain experiment data of QGP and hadronic matter produced from ultrarelativistic heavy ion collisions.The suppression of J/? production is an effective signal of the existence of QGP.Since the light meson-charmonium inelastic scattering in hadronic matter also causes the J/? suppression,it is very important to investigate the light meson-charmonium dissociation reactions,in order to figure out the characteristics of hadronic matter and verify the existence of QGP.We investigate the influence of temperature and energy on meson-charmonium dissociation reactions in hadronic matter.Based on Born approximation and quark-interchange mechanism,we calculate the charmonium dissociation cross sections in collsions with K,?,? and K^* with the temperature-dependent potential,quark-antiquark relative-motion wave functions and meson masses.We discover that the change of temperature influence the results of cross sections greatly.Medium effects are prominent.The temperature dependence of the peak cross sections is related to the meson radius,the confinement potential and the node of the ?? wave function.Although the ? meson and kaon have similar masses,the energy and temperature dependence of the ?-charmonium dissociation cross sections are quite different from those of the K-charmonium dissociation cross sections.For 0.6?T/Tc<1 the cross sections for the ?-charmonium dissociation reactions are larger than the cross sections for the ?-charmonium dissociation reactions.Comparing two channels of the ?-charmonium dissociation reactions,the spin-spin interaction causes a difference in the unpolarised cross sections for the two channels when the confinement potential gives similar contributions to the two channels.With the temperature-dependent meson masses,parametrized cross sections and meson distribution functions,we calculate the charmonium dissociation rates and discuss the contribution of different mesons to the dissociation of charmonium.The numerical results show that the rates generally increase with increasing temperature or decrease with increasing charmonium momentum.We also discover that the contribution of ? + ?? and ? + X_c can be neglected,but that of ? + J/? reactions cannot be neglected.The dissociation rates of three kinds of charmonia with ? are all very small.In the last three year's Pb-Pb collisions experiments at LHC,the CMS Collaboration and the ATLAS Collaboration discovered the unchanged prompt-J/? nuclear modification factor with increasing J/? transverse momentum for 10 GeV/c to 20 GeV/c.In terms of such high momentum charmonium,we need a new mechanism to explain this new phenomenon.The high energy charmonium collides with light mesons in hadronic matter,which produces quarks and antiquarks.The charm quark?anti-charm quark?fragments into charmed meson.Based on this mechanism,we derive the corresponding formula of cross section.Since the pion is the most in hadronic matter,we investigate the ?-charmonium dissociation reactions,where the quarks fragment into D⁺,D⁰,Ds⁺,D*⁺ and D*⁰ mesons.All the reactions are endothermic.Using the fragmentation functions and the temperature-dependent potential,meson masses and the quark-antiquark relative-motion wave functions,we obtain the temperature-dependent cross sections for ?-charmonium dissociation reactions.The results show that given a temperature and a difference between s^1/2 and the threshold energy,the cross section for the production of 0 is largest,the cross section for the production of + is smallest,and the cross section for ? + ?? ? H_c+ X or ? + ?_c? H_c+ X is larger than the one for ? + J/? ? H_c+ X.Furthermore,we calculate the corresponding charmonium dissociation rates in collisions with pion.We discover that the dissociation rate increases with increasing temperature and /or increasing charmonium momentum.Thus the ?-charmonium dissociation reactions governed by this mechanism cause the decreasing charmonium nuclear modification factor with increasing charmonium transverse momentum.This partly cancels out the increasing nuclear modification factor with increasing transverse momentum caused by the nuclear parton shadowing.Our new mechanism is necessary in order to explain the unchanged prompt-J/? nuclear modification factor with increasing J/? transverse momentum obtained from the experiments.