The role of proton-antiproton regeneration in the late stages of heavy-ion collisions

Abstract

We investigate the long-standing question of the effect of proton-antiproton annihilation on the (anti-)proton yield, while respecting detailed balance for the 5-body back-reaction for the first time in a full microscopic description of the late stages of heavy-ion collisions. This is achieved by employing a stochastic collision criterion in a hadronic transport approach (SMASH), which allows to treat arbitrary multi-particle reactions. It is used to account for the regeneration of (anti-)protons via $5\pi \to p\bar{p}$. Our results show that a back-reaction happens for a fraction of 15-20\% of all annihilations. Within a viscous hybrid approach Au+Au/Pb+Pb collisions from $\sqrt{s_{NN}}=17.3$ GeV$-5.02$ TeV are investigated and the quoted fraction is independent of the beam energy or centrality of the collision. Taking the back-reaction into account results in regeneration of half of the (anti-)proton yield that is lost due to annihilations at midrapidity. We also find that, concerning the multiplicities, treating the back-reaction as a chain of 2-body reactions is equivalent to a single 5-to-2 reaction.

6 pages, 4 figures

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• Cooper-Frye sampling with short-range repulsion
• Impact of hadronic interactions and conservation laws on cumulants of conserved charges in a dynamical model
• Using Baryonic Charge Balance Functions to Resolve Questions about the Baryo-Chemistry of the QGP
• Extension of the integrated hydrokinetic model to nuclear collision energies relevant for the RHIC Beam-Energy Scan program and the research program at GSI-FAIR
• Impact of Baryon anti-Baryon annihilation on hyperon ($\Lambda$, $\bar{\Lambda }$) production and apparent strangeness enhancement in $\bar{\Lambda }/\bar{p}$ in heavy ion collisions at SPS energy
• Particle spectra in the integrated hydrokinetic model at RHIC Beam-Energy-Scan energies