Particle Multiplicities in Nuclear Collisions at the LHC from Saturation Physics

TL;DR

This paper investigates how running coupling effects in saturation physics influence particle multiplicity predictions in lead-lead collisions at the LHC, providing updated estimates based on evolved gluon distributions.

Contribution

It introduces a refined approach incorporating running coupling in BK-JIMWLK equations to improve particle multiplicity predictions at LHC energies.

Findings

Predicted central multiplicity dN/dη ≈ 1390 at 5.5 TeV

Running coupling effects slow down the energy dependence of the saturation scale

Updated predictions differ from previous estimates based on fixed coupling models

Abstract

The inclusion of running coupling effects in the BK-JIMWLK evolution equations considerably reduces the energy dependence of the saturation scale with respect to previous estimates based on fits to HERA data. We discuss how such slowdown affects the expectations for particle multiplicities in Pb-Pb collisions at LHC energies. Our prediction is based on the use of k_t-factorization and on the use of unintegrated gluon distributions taken from the numerical solutions of the BK equation with running coupling. We obtain a central value dN/d\eta(sqrt{s}=5.5 TeV)(\eta=0)~1390.