Gravitational Wave Pathway to Testable Leptogenesis

TL;DR

This paper explores how gravitational wave observations can test a classically scale-invariant $B-L$ model that explains leptogenesis and baryon asymmetry, linking cosmological signals with particle physics.

Contribution

It demonstrates that current and future gravitational wave detectors can probe the parameter space of $B-L$ models responsible for leptogenesis, complementing collider searches.

Findings

Current LIGO-VIRGO limits exclude part of the $B-L$ parameter space.

Future GW detectors like Einstein Telescope can probe a wide range of $B-L$ scales.

Gravitational waves from phase transitions can serve as signatures of leptogenesis models.

Abstract

We analyze the classically scale-invariant $B-L$ model in the context of resonant leptogenesis with the recently proposed mass-gain mechanism. The $B-L$ symmetry breaking in this scenario is associated with a strong first order phase transition that gives rise to detectable gravitational waves (GWs) via bubble collisions. The same $B-L$ symmetry breaking also gives Majorana mass to right-handed neutrinos inside the bubbles, and their out of equilibrium decays can produce the observed baryon asymmetry of the Universe via leptogenesis. We show that the current LIGO-VIRGO limit on stochastic GW background already excludes part of the $B-L$ parameter space, complementary to the collider searches for heavy $Z^{\prime}$ resonances. Moreover, future GW experiments like Einstein Telescope and Cosmic Explorer can effectively probe the parameter space of leptogenesis over a wide range of the $B-L$ symmetry-breaking scales and gauge coupling values.