Bjorken initial energy density estimation in Xe-Xe collisions at $\sqrt{s_{NN}} = 5.44$ TeV using ALICE

TL;DR

This study estimates the initial energy density in Xe-Xe collisions at 5.44 TeV using the Bjorken formula, comparing different assumptions and with Pb-Pb collisions, to understand quark-gluon plasma formation.

Contribution

It introduces a comparative analysis of initial energy density estimation methods in Xe-Xe collisions and evaluates their consistency with Pb-Pb collision data.

Findings

Energy density varies with centrality and assumptions.

Xe-Xe system size is smaller than Pb-Pb at similar energies.

Case III provides more consistent energy density estimates.

Abstract

The Bjorken initial energy density ($\epsilon_{B}$) has been estimated in different centrality classes in Xe-Xe collisions using Bjorken formula. Three different cases have been considered. In Case I, we have fixed the formation time ($\tau_{0}$) and varied the area of overlap region ($A_{overlap}$). In Case II, we have fixed both $\tau_{0}$ and $A_{overlap}$ and we have varied both $\tau_{0}$ and $A_{overlap}$ in Case III. We observed that the $\epsilon_{B}$ is first increasing and then decreasing while going from central to peripheral collisions in Case I whereas it is decreasing in Case II and III, as expected. The $\epsilon_{B}$ value for top central and mid central collisions in Case II and for all centrality classes in Case III are greater than 1 $GeV/(fm)^{3}$, indicating the possibility of QGP medium formation respectively. The $\epsilon_{B}$ results of the Pb-Pb at $\sqrt{s_{NN}} = 2.76$ and 5.02 TeV are compared. In Case II, it is observed that in the centrality class (0-5)%, the $\epsilon_{B}$ value in Xe-Xe collisions at $\sqrt{s_{NN}} = 5.44$ TeV is 34.66% less than in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV and 57.12% less than at 5.02 TeV. This may be interpreted as, the system size in Xe-Xe collisions at $\sqrt{s_{NN}} = 5.44$ TeV is 34.66% smaller than in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV and 57.12% smaller than at 5.02 TeV. Similarly in Case III in the centrality class (0-5)%, the $\epsilon_{B}$ value in Xe-Xe collisions at $\sqrt{s_{NN}} = 5.44$ TeV is 3.22% more than in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV and 32.18% less than at 5.02 TeV. This may be interpreted as, the system size in Xe-Xe collisions at $\sqrt{s_{NN}} = 5.44$ TeV is 3.22% bigger than in Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV and 32.18% smaller than at 5.02 TeV. The results obtained in the Case III seems more suitable than Case II.