Probing baryogenesis with neutron-antineutron oscillations

TL;DR

This paper investigates how neutron-antineutron oscillations could inform baryogenesis, analyzing different scenarios and constraints to identify conditions under which baryon asymmetry could be generated or washed out.

Contribution

It provides a comprehensive analysis of baryogenesis implications from neutron-antineutron oscillation observations, including model-independent and simplified model approaches with CP violation considerations.

Findings

Small mass hierarchy leads to strong washout of baryon asymmetry.

Large hierarchy allows successful baryogenesis within experimental constraints.

Current and future experiments can probe the parameter space relevant for baryogenesis.

Abstract

In the near future, the Deep Underground Neutrino Experiment and the European Spallation Source aim to reach unprecedented sensitivity in the search for neutron-antineutron ($n\text{-}\bar{n}$) oscillations, whose observation would directly imply $|\Delta B| = 2$ violation and hence might hint towards a close link to the mechanism behind the observed baryon asymmetry of the Universe. In this work, we explore the consequences of such a discovery for baryogenesis first within a model-independent effective field theory approach. We then refine our analysis by including a source of CP violation and different hierarchies between the scales of new physics using a simplified model. We analyse the implication for baryogenesis in different scenarios and confront our results with complementary experimental constraints from dinucleon decay, LHC, and meson oscillations. We find that for a small mass hierarchy between the new degrees of freedom, an observable rate for $n\text{-}\bar{n}$ oscillation would imply that the washout processes are too strong to generate any sizeable baryon asymmetry, even if the CP violation is maximal. On the other hand, for a large hierarchy between the new degrees of freedom, our analysis shows that successful baryogenesis can occur over a large part of the parameter space, opening the window to be probed by current and future colliders and upcoming $n\text{-}\bar{n}$ oscillation searches.