Yayun He, Long-Gang Pang, and Xin-Nian Wang, Gradient Tomography of Jet Quenching in Heavy-Ion Collisions, Phys. Rev. Lett. 125, 122301 (2020)

Transverse momentum broadening and energy loss of a propagating parton are dictated by the space-time profile of the jet transport coefficient in a dense QCD medium. The spatial gradient of the jet transport coefficient in the direction perpendicular to the parton propagation can lead to a drift and asymmetry in parton transverse momentum distribution. Such an asymmetry depends on both the spatial position along the transverse gradient and path length of a propagating parton as shown by numerical solutions of the Boltzmann transport in the simplified form of a drift-diffusion equation. In high-energy heavy-ion collisions, this asymmetry with respect to a plane defined by the beam and trigger particle (photon, hadron, or jet) with a given orientation relative to the event plane is shown to be closely related to the transverse position of the initial jet production in full event-by-event simulations within the linear Boltzmann transport model. Such a gradient tomography can be used to localize the initial jet production position for more detailed study of jet quenching and properties of the quark-gluon plasma.