title: Nonthermal p/π ratio at LHC as a consequence of hadronic final state interactions.
abstract: Recent LHC data on Pb+Pb reactions at sqrt[s](NN) = 2.7 TeV suggests that the p/π is incompatible with thermal models. We explore several hadron ratios (K/π, p/π, Λ/π, Ξ/π) within a hydrodynamic model with a hadronic after burner, namely the ultrarelativistic quantum molecular dynamics model 3.3, and show that the deviations can be understood as a final state effect. We propose the p/π as an observable sensitive on whether final state interactions take place or not. The measured values of the hadron ratios do then allow us to gauge the transition energy density from hydrodynamics to the Boltzmann description. We find that the data can be explained with transition energy densities of 840 ± 150 MeV/fm(3).
authors.affiliation: Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720, USA and Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Steinheimer
authors.affiliation: SUBATECH, UMR 6457, Université de Nantes, Ecole des Mines de Nantes, IN2P3/CNRS. 4 rue Alfred Kastler, 44307 Nantes cedex 3, France and Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Aichelin
authors.affiliation: Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität, Max-von-Laue-Strasse 1, 60438 Frankfurt am Main, Germany and Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universität, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Bleicher