Fingerprint of GeV scale right-handed neutrinos on inflationary gravitational waves and PTA data

TL;DR

This paper links right-handed neutrinos at the GeV scale to inflationary gravitational waves, explaining recent PTA data and predicting testable signals for future GW detectors and collider experiments.

Contribution

It demonstrates that seesaw mechanisms with GeV-scale right-handed neutrinos can produce observable gravitational wave signatures compatible with PTA findings and linked to low-scale leptogenesis.

Findings

PTA data compatible with blue-tilted inflationary GWs from GeV-scale RHNs

Predicted GW spectral features testable by future LIGO runs

GeV-scale RHNs can be probed in collider experiments

Abstract

We show that the seesaw mechanisms that exhibit right-handed neutrino mass-dependent non-standard post-inflationary cosmology make blue-tilted inflationary gravitational waves (GW) compatible with the recent findings of nHz stochastic GW background by the pulsar-timing arrays (PTAs) for high reheating temperatures. The right-handed neutrino (RHN) mass scale has to be $\mathcal{O}(\rm GeV)$. Remarkably, such a scenario produces a correlated signature testable by the future LIGO run. In addition to contributing to the active neutrino masses, $\mathcal{O}(\rm GeV)$ RHNs generate baryon asymmetry of the universe via low-scale-leptogenesis. They can be searched for in collider experiments. Therefore, the recent detection by PTAs is not only exciting for GWs in the nHz range; it paves the way to test and constrain well-studied mechanisms, such as seesaws, with a low-frequency and a correlated measurement of high-frequency GW spectral features, complementary to particle physics searches.