Photon multiplicity measurements at forward rapidity in the ALICE experiment at CERN

TL;DR

This paper reports the first photon multiplicity measurements at forward rapidity in proton-proton collisions at 7 TeV at the LHC, revealing that models like PYTHIA, PHOJET, and HERWIG do not fully explain the data.

Contribution

First measurement of photon multiplicity at forward rapidity in pp collisions at 7 TeV, with results challenging existing models.

Findings

Photon multiplicity distribution fits a double Negative Binomial Distribution.

Average photon multiplicity increases logarithmically with collision energy.

Current models do not accurately describe the measured data.

Abstract

We present the first preliminary results on photon multiplicity measurements at LHC at forward pseudorapidity (2.3 $\textless$ $\eta$ $\textless$ 3.9) in proton-proton ($pp$) collisions at $\sqrt{s}$ = 7 TeV. The multiplicity distribution is found to be reasonably well explained by a double Negative Binomial Distribution (NBD). The average photon multiplicity increases logarithmically with $\sqrt{s}$. It is found that none of the models we used (PYTHIA6D6T, PHOJET, and HERWIG) could explain the data.