Jet Tomography of Harmonic Fluctuations in the Initial Condition of Heavy Ion Collisions

TL;DR

This paper investigates how harmonic fluctuations in initial conditions affect jet azimuthal anisotropy in heavy ion collisions, linking jet response to observed correlation structures.

Contribution

It introduces a cumulant expansion approach to model harmonic fluctuations and connects jet response with bulk matter expansion to explain the hard-ridge phenomenon.

Findings

Jet response to initial fluctuations is quantified by response coefficients.

Hard-soft azimuthal correlations show a narrow near-side peak.

The model explains the dominant contribution to the experimental hard-ridge.

Abstract

In this paper we study the jet response (particularly azimuthal anisotropy) as a hard probe of the harmonic fluctuations in the initial condition of central heavy ion collisions. By implementing the fluctuations via cumulant expansion for various harmonics quantified by $\epsilon_n$ and using the geometric model for jet energy loss, we compute the response $\chi^h_n=v_n/\epsilon_n$. Combining these results with the known hydrodynamic response of the bulk matter expansion in the literature, we show that the hard-soft azimuthal correlation arising from their respective responses to the common geometric fluctuations reveals a robust and narrow near-side peak that may provide the dominant contribution to the "hard-ridge" observed in experimental data.