Quarkonia disintegration due to time dependence of the qq̄ potential in relativistic heavy-ion collisions

Abstract

Rapid thermalization in ultra-relativistic heavy-ion collisions leads to fast changing potential between a heavy quark and antiquark from zero temperature potential to the finite temperature one. Time dependent perturbation theory can then be used to calculate the survival probability of the initial quarkonium state. In view of very short time scales of thermalization at RHIC and LHC energies, we calculate the survival probability of J/ψ and Υ using sudden approximation. Our results show that quarkonium decay may be significant even when temperature of QGP remains low enough so that the conventional quarkonium melting due to Debye screening is ineffective.PACS numbers: PACS numbers: 11.27.+d, 14.40.Lb, 12.38.Mh Suppression of heavy quarkonia as a signal for the quark-gluon plasma phase in relativistic heavy-ion collisions has been investigated intensively since the original proposal by Matsui and Satz [1]. The underlying physical picture of this suppression is that due to deconfinment, potential between qq gets Debye screened, resulting in the swelling of quarkonia. If the Debye screening length of the medium is less than the radius of quarkonia, then qq may not form bound states, leading to melting of the initial quarkonium. Due to this melting, the yield of quarkonia will be suppressed. This was proposed as a signature of QGP and has been observed experimentally [2]. However, there are other factors too that can lead to the suppression of J/ψ because of which it has not been possible to use J/ψ suppression as a clean signal for QGP.In the above picture, suppression of quarkonia occurs when the temperature of QGP achieves a certain value, T D , so that the Debye screening melts the quarkonium bound state. Thus, if the temperature remains smaller than T D , so that Debye screening length remains larger than the quarkonia size, no suppression is expected. This type of picture is consistent with the adiabatic evolution of a quantum state under changing potential. Original quarkonia has a wave function appropriate for zero temperature potential between a q andq. If the environment of the quarkonium changes to a finite temperature QGP adiabatically, with Debye screened potential, the final state will evolve to the quarkonium state corresponding to the finite temperature potential. If temperature remains below T D , quarkonium wave function changes (adiabatically) but it survives as the quarkonium.We question this assumption of adiabatic evolution for ultra-relativistic heavy-ion collisions, such as at RHIC, and especially at LHC. At such energies, it is possible that thermalization is achieved in a very short time, about 0.25 fm for RHIC and even smaller about 0.1 fm for * Electronic address: partha@iopb.res.in † Electronic address: ajit@iopb.res.in LHC [3]. Even conservatively, thermalization is achieved within 1 fm as suggested by the elliptic flow measurements [4]. For J/ψ and even for Υ, typical time scale of qq dynamics will be at least 1-2 fm from the size of the bound state and the fact that qq have non-r...

Dissociation of heavy quarkonia in a weak magnetic field

“…Moreover, lattice studies have also shown that the potential may have a sizable imaginary part [22]. There are, however, other processes that may cause the depopulation of the resonance states either through the transition from ground state to the excited states during the nonadiabatic evolution of quarkonia [23] or through the swelling or shrinking of states due to the Brownian motion of QQ states in the parton plasma [24]. Very recently the change in the properties of heavy quarkonia immersed in a weakly coupled thermal QCD medium has been described by hard thermal loop (HTL) permittivity [25].…”

Dissociation of heavy quarkonium states in rapidly varying strong magnetic field

“…We have investigated the time evolution of spatial wave functions of quarkonia and therefore have not considered the spin-magnetic field interaction into account for the current article. The non-adiabatic evolution previously has been addressed in the context of evolving QGP [17] and also in the context of rapid thermalisation [18].…”