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

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.