High Energy Sphalerons for Baryogenesis at Low Temperatures

TL;DR

This paper explores how low-temperature reheating in the early universe can still produce baryon asymmetry through high-energy sphaleron processes, potentially detectable in experiments.

Contribution

It introduces a scenario where baryogenesis occurs at low reheating temperatures via high-energy sphaleron interactions, extending the Standard Model to enable this process.

Findings

Baryogenesis feasible at reheating temperatures as low as 0.1-1 GeV.

High-energy collisions can surpass sphaleron mass thresholds.

Experimental probes in colliders and cosmic rays are possible.

Abstract

We discuss baryogenesis in scenarios where the Universe is reheated to temperatures $\lesssim 100\,$GeV by the decay of long-lived massive particles into energetic SM particles. Before its thermalization, the center-of-mass energy in collisions between such a particle and a particle from the ambient plasma can be higher than the typical sphaleron mass, even if the temperature of the plasma itself is much lower. Optimistic estimates for the high energy enhancement of the sphaleron cross section suggest that successful baryogenesis is possible for reheating temperatures as low as $0.1\text{-}1\,$GeV. With a simple extension of the SM, sufficient baryon production can be achieved even if more pessimistic results for the sphaleron rate are correct. In both cases this scenario can be probed in collider and cosmic-ray experiments. We briefly discuss the possible origin of the required CP violation.