Direct gamma and gamma-jet measurement capability of ATLAS for Pb+Pb collisions

TL;DR

The ATLAS detector can effectively distinguish photons from hadrons in heavy-ion collisions, enabling precise measurements of direct photons and gamma-jets, including non-isolated photons from fragmentation or medium effects.

Contribution

This paper demonstrates ATLAS's capability to measure direct photons and gamma-jets in Pb+Pb collisions, highlighting its unique ability to access non-isolated photon signals.

Findings

Successful separation of photons and hadrons over wide kinematic ranges.

First measurement prospects of direct photons in Pb+Pb collisions at 5.5 TeV.

Potential to study medium effects via non-isolated photon detection.

Abstract

The ATLAS detector at the LHC is capable of efficiently separating photons and neutral hadrons based on their shower shapes over a wide range in eta, phi, ET, either in addition to or instead of isolation cuts. This provides ATLAS with a unique strength for direct photon and gamma-jet physics as well as access to the unique capability to measure non-isolated photons from fragmentation or from the medium. We present a first look at the ATLAS direct photon measurement capabilities in Pb+Pb and, for reference, p+p collisions at sqrt(sNN)=5.5 TeV over the region |eta|<2.4.