Observing Transverse Momentum Broadening from TEECs in Heavy Ion Collisions

Abstract

We study the azimuthal dependence of transverse energy-energy correlators (TEECs) in dijet events in heavy-ion collisions. In the back-to-back region this observable resolves the energy flow around $ϕ=π$ and is sensitive to medium-induced momentum broadening and the response of the medium. To isolate final-state effects, we consider a quark-antiquark pair produced in a colour-singlet hard process and propagating through a homogeneous background medium. Starting from the vacuum TMD factorization formula, we combine NLL$'$ resummation with medium modifications at first order in the strong coupling. For the parameters studied, (classical) momentum broadening lowers the back-to-back peak and leaves the distribution elsewhere nearly unchanged, while radiative corrections significantly suppress the peak further and enhance larger angular decorrelations. We additionally include the medium response sourced by each jet, as a mean energy flow. This spreads the deposited energy over the whole azimuth, so that the contribution to the TEEC varies slowly across the back-to-back region, is small at the peak and grows toward larger angles.