Fingerprints of GeV scale right-handed neutrinos on inflationary gravitational waves and PTA data
Satyabrata Datta, Rome Samanta
Abstract
We show that the seesaw mechanisms that exhibit right-handed neutrino mass-dependent nonstandard postinflationary cosmology make blue-tilted inflationary gravitational waves (GWs) compatible with the recent findings of nanohertz stochastic GW background by the pulsar-timing arrays (PTAs) for high reheating temperatures. The right-handed neutrino (RHN) mass scale has to be $\mathcal{O}(\mathrm{GeV})$. Remarkably, such a scenario produces a correlated signature testable by the future LIGO run. In addition to contributing to the active neutrino masses, $\mathcal{O}(\mathrm{GeV})$ 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 nanohertz 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.