Understanding the $p/\pi$ ratio at LHC due to QCD mass spectrum

Abstract

Thermal fits have consistently reproduced the experimental particles yields of heavy ion collisions, however, the proton to pion ratio from ALICE Pb+Pb $\sqrt{s_{NN}}=2.76$ TeV is over-predicted by thermal models- known at the $p/\pi$ puzzle. Here we test the relevance of the extended mass spectrum, i.e., include Hagedorn states (resonances that follow an exponential mass spectrum and have very short life times) on the $p/\pi$ puzzle. We find that the extended mass spectrum is able to reproduce particle ratios at both RHIC and the LHC as well as being able to match the lower $p/\pi$ ratio at the LHC through dynamical chemical equilibration.