Towards detailed tomography of high energy heavy-ion collisions by $\gamma$-jet

TL;DR

This paper investigates the energy imbalance between prompt photons and jets in high-energy Pb+Pb collisions, demonstrating how it reveals detailed information about the quark-gluon plasma through $ ext{γ}$-jet tomography and correlations.

Contribution

It introduces a method to use $ ext{γ}$-jet imbalance and azimuthal correlations to perform detailed tomography of the partonic medium in heavy-ion collisions.

Findings

Jet energy loss increases with collision centrality.

Imbalance ratio $x_{j ext{γ}}$ depends on production position and direction.

$ ext{γ}$-hadron correlations probe medium response.

Abstract

Within a multi-phase transport (AMPT) model with string melting scenario, the transverse momentum imbalance between prompt photon and jet is studied in Pb+Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 2.76 TeV. Jet loses more energy in more central collisions due to strong partonic interactions between jet parton shower and partonic matter, which is more significant than due to hadronic interactions only. The hadronization and final-state hadronic interactions have little influences on the imbalance. The imbalance ratio $x_{j\gamma}$ is sensitive to both production position and passing direction of $\gamma$-jet, which provides an opportunity to do detail $\gamma$-jet tomography on the formed partonic matter by selecting different $x_{j\gamma}$ ranges. It is also proposed that $\gamma$-hadron azimuthal correlation associated with photon+jet is a probe to see the medium responses to different $\gamma$-jet production configurations.