Probing hot and dense matter production in heavy ion collisions via neutral mesons and photons with the ALICE detector at the LHC

TL;DR

This paper reviews measurements of neutral mesons and photons in heavy-ion and proton-proton collisions at the LHC, providing insights into the properties of the Quark Gluon Plasma through suppression and enhancement patterns.

Contribution

It presents new experimental data on photon and neutral meson production in heavy-ion collisions, advancing understanding of jet quenching and thermal photon sources.

Findings

Suppression of high pT hadrons indicates parton energy loss in QGP.

No suppression observed for high pT direct photons.

Potential thermal photon enhancement at low pT.

Abstract

One of the key signatures of the Quark Gluon Plasma (QGP) is the modification of hadron and direct photon spectra in heavy-ion collisions as compared to proton-proton (pp) collisions. Suppression of hadron production at high transverse momenta in heavy-ion collisions can be explained by the energy loss of the partons produced in the hard scattering processes which traverse the hot and dense QCD matter. The dependence of the observed suppression on the transverse momentum (pT) of the measured hadron towards higher pT is an important input for the theoretical understanding of jet quenching effects in the QGP and the nature of energy loss. Another key observable which has helped establish the energy loss picture, is high pT direct photon production for which no suppression is expected. For low pT photon production, it is expected that thermal sources will lead to enhancement of direct photons. We report an overview of photon and neutral meson production measurements by the ALICE experiment at the LHC in heavy-ion and pp collisions.