Smooth matching of $\hat{q}$ from hadronic to quark and gluon degrees of freedom

TL;DR

This paper investigates the transition of the jet transport coefficient q/T^3 from hadronic to quark-gluon degrees of freedom, proposing a smooth crossover when considering experimental uncertainties and higher pseudo-critical temperatures.

Contribution

It demonstrates that incorporating experimental errors and a higher pseudo-critical temperature allows for a smooth q/T^3 transition between phases, challenging the notion of a large jump.

Findings

q/T^3 can transition smoothly with experimental error considerations

Significant q/T^3 enhancement at finite baryon chemical potential

Identifies issues with shear viscosity and jet transport coefficient relationship

Abstract

One of the key signatures of the Quark Gluon Plasma (QGP) is the energy loss of high momentum particles as they traverse the strongly interacting medium. The energy loss of these particles is governed by the jet transport coefficient $\hat{q}/T^3$, wherein it has been thought that there is a large jump as the system transitions between the hadron gas and Quark Gluon Plasma phases. Here we calculate $\hat{q}/T^3$ within the Hadron Resonance Gas (HRG) model with the particle list PDG16+ and find that, if one incorporates the experimental error in the hadronic calculation of $\hat{q}/T^3$ and assumes a higher pseudo-critical temperature, then a smooth transition from the hadron gas phase into the Quark Gluon Plasma phase is possible. We also find a significant enhancement in $\hat{q}/T^3$ at finite baryon chemical potential and find issues with the relationship between the shear viscosity and the jet transport coefficient within a hadron gas phase.