Event-by-Event Jet Quenching

TL;DR

This paper compares event-by-event and averaged fireball models for jet quenching in quark-gluon plasma, revealing that fluctuations significantly affect transport coefficients and could enable spatial tomography of the fireball.

Contribution

It introduces an event-by-event jet quenching analysis with realistic inhomogeneous fireballs, highlighting the impact of fluctuations on transport coefficient extraction and potential fireball tomography.

Findings

Event-by-event analysis fits R_AA well within experimental errors.

Transport coefficient qhat is underestimated by averaged models by up to 50%.

Residual deviations in v_2 and correlations suggest possible spatial tomography.

Abstract

High momentum jets and hadrons can be used as probes for the quark gluon plasma (QGP) formed in nuclear collisions at high energies. We investigate the influence of fluctuations in the fireball on jet quenching observables by comparing propagation of light quarks and gluons through averaged, smooth QGP fireballs with event-by-event jet quenching using realistic inhomogeneous fireballs. We find that the transverse momentum and impact parameter dependence of the nuclear modification factor R_AA can be fit well in an event-by-event quenching scenario within experimental errors. However the transport coefficient qhat extracted from fits to the measured nuclear modification factor R_AA in averaged fireballs underestimates the value from event-by-event calculations by up to 50%. On the other hand, after adjusting qhat to fit R_AA in the event-by-event analysis we find residual deviations in the azimuthal asymmetry v_2 and in two-particle correlations, that provide a possible faint signature for a spatial tomography of the fireball.