Electromagnetic radiation and collectivity in small quark-gluon droplets

TL;DR

This paper investigates photon production and flow in small quark-gluon plasma droplets created in p+Pb collisions, revealing rapidity-dependent thermal effects and anisotropic flow that shed light on the system's longitudinal dynamics.

Contribution

It introduces a (3+1)D viscous hydrodynamic model to analyze rapidity-dependent photon observables in small collision systems, highlighting the interplay of initial and final state effects.

Findings

Rapidity-dependent thermal photon enhancement observed.

Anisotropic flow coefficients vary with rapidity.

Results suggest complex longitudinal dynamics in small QGP droplets.

Abstract

We study the multiplicity and rapidity dependence of thermal and prompt photon production in p+Pb collisions at 5.02 TeV, using a (3+1)D viscous hydrodynamic framework. Direct photon anisotropic flow coefficients $v^\gamma_{2,3}$ and nuclear modification factor $R^\gamma_\mathrm{pPb}(p_T)$ are presented in both the p-going (backward) and the Pb-going (forward) directions. The interplay between initial state cold nuclear effect and final state thermal enhancement at different rapidity regions is discussed. The proposed rapidity dependent thermal photon enhancement and direct photon anisotropic flow observables can elucidate non-trivial longitudinal dynamics of hot quark-gluon plasma droplets created in small collision systems.