Mesogenesis through the Ephemeral Dark Decay of Beauty

TL;DR

This paper proposes a novel Mesogenesis mechanism involving early Universe dark sector interactions with $B$ mesons, compatible with current experimental constraints and potentially observable in future experiments.

Contribution

It introduces a scenario where an ultralight scalar enables early Universe dark sector decays of $B$ mesons, explaining baryon asymmetry without conflicting with flavor and collider data.

Findings

Dark decay channel dominates in the early Universe due to muon density effects.

Model remains consistent with LHC constraints on heavy bosons.

Potential signals include displaced vertices, long-range forces, and neutron star mergers.

Abstract

Mesogenesis provides a path for generating the baryon asymmetry of the Universe, using only the CP violation furnished by the Standard Model in the decay of $B$ mesons. While this is an intriguing possibility, it is largely constrained by the data on $B$ meson branching fractions into baryons and missing energy carried into the dark sector. We point out that it is possible to make this branching fraction dominant only in the early Universe, through an ultralight scalar coupled to the dark sector and the Standard Model leptons. A scenario is examined where the thermal density of muons in the early Universe temporarily lowers the mass of a dark fermion, allowing for efficient $B$ meson decays. This `dark' decay channel is shut off later when the muon number density falls, making the scenario compatible with flavor data. Our model can be consistent with the LHC constraints on color-charged heavy bosons required to implement Mesogenesis; such states may be discovered in the future runs as their masses cannot be far above the current bounds. We also outline other possible signals, which can arise in future displaced vertex searches, long range force searches, and observations of neutron star binary mergers.