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

We investigate the long-standing question of the effect of proton-antiproton annihilation on the (anti-)proton yield, while respecting detailed balance for the five-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 is used to account for the regeneration of (anti-)protons via 5 pi -> p (p) over bar. We investigate Au+Au and Pb+Pb collisions from root S-NN = 17.3 GeV - 5.02 TeV in a viscous hybrid approach. Our results show that back-reactions happen for a fraction of 15%-20% of all annihilations, independent of the beam energy or centrality of the system. The inclusion of the back-reaction results in the regeneration of half of the (anti-)proton yield lost to annihilations at midrapidity. We also find that, concerning the multiplicities, treating the back-reaction as a chain of two-body reactions is equivalent to a single 5-to-2 reaction.

Automated summary

In this study, the long-standing question of the effect of proton-antiproton annihilation on the (anti-)proton yield is investigated. The detailed balance for the five-body back-reaction is respected for the first time in a full microscopic description of the late stages of heavy-ion collisions. The results show that only 15%-20% of the (anti-)proton annihilation reactions involve back-reactions, and the regeneration of half of the (anti-)proton yield lost to annihilations is observed.