2025/04/21 by Zafri A. Borboruah, Frank F. Deppisch, Borboruah, Zafri A. +5 · 4 citations
Physics and Astronomy · #Neutrino Physics Research #Particle physics theoretical and experimental studies #Astrophysics and Cosmic Phenomena
paper · pdf · doi:10.48550/arxiv.2504.15374
We analyze the damping of inflationary gravitational waves (GW) that re-enter the Hubble horizon before or during a post-inflationary era dominated by a meta-stable, right-handed neutrino (RHN), whose out-of-equilibrium decay releases entropy. Within a minimal type-I seesaw extension of the Standard Model (SM), we explore the conditions under which the population of thermally produced RHNs remain long-lived and cause a period of matter-domination. We find that the suppression of the GW spectrum occurs above a characteristic frequency determined by the RHN mass and active-sterile mixing. For RHN masses in the range 0.1-10 GeV and mixing 10-12 \lesssim |VeN|2 \lesssim 10-5, we estimate such characteristic frequencies and the signal-to-noise ratio to assess the detection prospects in GW observatories such as THEIA, μ-ARES, LISA, BBO and ET. Additionally we use LIGO data to put upper bounds on the reheating temperature after inflation, for a given blue-tilted GW spectrum. We find complementarity between GW signals and laboratory searches in SHiP, DUNE and LEGEND-1000. Notably, RHN masses of 0.2-2 GeV and mixing 10-10 \lesssim |VeN|2 \lesssim 10-7 are testable in both laboratory experiments and GW observations. Additionally, GW experiments can probe the canonical seesaw regime of light neutrino mass generation, a region largely inaccessible to laboratory searches.