Probing low scale leptogenesis through gravitational wave

TL;DR

This paper explores how low-scale leptogenesis within a $U(1)_{B-L}$ extended Standard Model can be probed through gravitational waves generated by cosmological phase transitions, linking particle physics and gravitational wave astronomy.

Contribution

It systematically analyzes TeV-scale leptogenesis, including flavor effects and RHN production channels, highlighting the potential of gravitational wave signals to probe new physics beyond collider reach.

Findings

A $U(1)_{B-L}$ gauge boson around 10 TeV can account for baryon asymmetry.

Detectable stochastic gravitational wave background can originate from $U(1)_{B-L}$ phase transition.

The parameter space for successful leptogenesis and GW detection extends beyond current collider sensitivity.

Abstract

The quest for a common origin of neutrino mass and baryogenesis is one of the longstanding goals in particle physics. A minimal gauge extension of the Standard Model by $U(1)_{\rm B-L}$ symmetry provides a unique scenario to explain the tiny mass of neutrinos as well as the observed baryon asymmetry, both by virtue of three right-handed neutrinos (RHNs). Additionally, the $U(1)_{\rm B-L}$ breaking scalar that generates mass of the RHNs can produce a stochastic gravitational wave background (SGWB) via cosmological first-order phase transition. In this work, we systematically investigate TeV-scale leptogenesis considering flavor effects that are crucial in low temperature regime. We also explore all possible RHN production channels which can have significant impact on the abundance of RHNs, depending on the value of $U(1)_{\rm B-L}$ gauge coupling. We demonstrate that the strong dependence of $U(1)_{\rm B-L}$ gauge sector on the baryon asymmetry as well as SGWB production can be utilized to probe a region of the model parameter space. In particular, we find that $U(1)_{\rm B-L}$ gauge boson with mass $\sim 10\,\rm TeV$ and gauge coupling $\sim 0.1$ can explain the observed baryon asymmetry and produces detectable SGWB in future detectors as well. Importantly, this region falls beyond the reach of the current collider sensitivity.