Jet tomography of harmonic fluctuations in the initial condition of heavy ion collisions

In this Letter 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 ϵn and using the geometric model for jet energy loss, we compute the response χnh=vn/ϵn. 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.