EPOS LHC: Test of collective hadronization with data measured at the CERN Large Hadron Collider

Abstract

Epos is a Monte Carlo event generator for minimum bias hadronic interactions, used for both heavy ion interactions and cosmic ray air shower simulations. Since the last public release in 2009, the Large Hadron Collider (LHC) experiments have provided a number of very interesting data sets comprising minimum bias $p\text{\ensuremath{-}}p,\phantom{\rule{0.16em}{0ex}}p$-Pb, and Pb-Pb interactions. We describe the changes required to the model to reproduce in detail the new data available from the LHC and the consequences in the interpretation of these data. In particular we discuss the effect of the collective hadronization in $p\text{\ensuremath{-}}p$ scattering. A different parametrization of flow has been introduced in the case of a small volume with high density of thermalized matter (core) reached in $p\text{\ensuremath{-}}p$ compared to large volume produced in heavy ion collisions. Both parametrizations depend only on the geometry and the amount of secondary particles entering in the core and not on the beam mass or energy. The transition between the two flow regimes can be tested with $p$-Pb data. Epos LHC is able to reproduce all minimum bias results for all particles with transverse momentum from ${p}_{\mathrm{t}}=0$ to a few GeV/$c$.