Anti-Proton Evolution in Little Bangs and Big Bang

TL;DR

This paper models anti-proton and proton abundances in both heavy-ion collisions and the early universe, showing a small ratio change in collisions and long equilibrium in the Big Bang, addressing the anti-proton puzzle.

Contribution

It provides a unified Boltzmann equation framework to compare anti-proton evolution in Little Bangs and Big Bang scenarios, clarifying their different behaviors.

Findings

Small anti-proton to proton ratio change in heavy-ion collisions.

Long-lived anti-baryons in the early universe.

Mapping of cosmic matter evolution in the phase diagram.

Abstract

The abundances of anti-protons and protons are considered within momentum-integrated Boltzmann equations describing Little Bangs, i.e., fireballs created in relativistic heavy-ion collisions. Despite of a large anti-proton annihilation cross section we find a small drop of the ratio of anti-protons to protons from 170 MeV (chemical freeze-out temperature) till 100 MeV (kinetic freeze-out temperature) for CERN-SPS and BNL-RHIC energies thus corroborating the solution of the previously exposed "ani-proton puzzle". In contrast, the Big Bang evolves so slowly that the anti-baryons are kept for a long time in equilibrium resulting in an exceedingly small fraction. The adiabatic path of cosmic matter in the phase diagram of strongly interacting matter is mapped out.