Nuclear modification factor in an anisotropic quark-gluon plasma

Abstract

We calculate the nuclear modification factor (R AA ) of light hadrons by taking into account the initial state momentum anisotropy of the quark gluon plasma (QGP) expected to be formed in relativistic heavy ion collisions. Such an anisotropy can result from the initial rapid longitudinal expansion of the matter. A phenomenological model for the space time evolution of the anisotropic QGP is used to obtain the time dependence of the anisotropy parameter ξ and the hard momentum scale, p hard . The result is then compared with the PHENIX experimental data to constrain the isotropization time scale, τ iso for fixed initial conditions (FIC). It is shown that the extracted value of τ iso lies in the range 0.5 ≤ τ iso ≤ 1.5. However, using fixed final multiplicity (FFM) condition does not lead to any firm conclusion about the extraction of the isotropization time. The present calculation is also extended to contrast with the recent measurement of nuclear modification factor by ALICE collaboration at √ s = 2.76 TeV. It is argued that in the present approach, the extraction of τ iso at this energy is uncertain and, therfore, refinement of the model is necessary. The sensitivity of the results on the initial conditions has been discussed. We also present the nuclear modification factor at LHC energies with √ s = 5.5 TeV.

Gluon dissociation ofJ/ψin anisotropic quark-gluon plasma

“…It is to be noted that apart from this mechanism of suppression, there are other mechanisms by which J/ψ can be suppressed [3]. All these possible processes should be taken into account and then be compared with the experimental data of transverse momentum distribution of J/ψ to extract the isotropization time τ iso as has been done in case of photons [12] and nuclear modification of light hadrons [16].…”

“…[3] , i.e., T i = 550 MeV and τ i = 0.7 fm/c. For other set (set II) the initial temperature (time) has been calculated using the measured multiplicities at RHIC energies [16] and is given by T i = 440 MeV corresponding to τ i = 0.15 fm/c. At LHC energies we use the initial conditions: T i = 820 MeV and τ i = 0.5 fm/c.…”

“…Recently, the authors in Ref. [16] calculated the nuclear modification factor for light hadrons assuming an anisotropic QGP and showed how the isotropization time can be extracted by comparing with the experimental data. Most importantly, the heavy quark potential has been calculated in Ref.…”

Some Aspects of Anisotropic Quark-Gluon Plasma

“…Equation (44) has been used to calculate the survival probability. Figure 5 describes the survival probability of / for various values of the isotropization time iso at RHIC energy.…”

“…Effects of anisotropy on photon and dilepton yields have been investigated rigorously in [16,[39][40][41][42][43]. Recently, the authors in [44] calculated the nuclear modification factor for light hadrons assuming an anisotropic QGP and showed how the isotropization time can be extracted by comparing with the experimental data.…”