PPC 2024: XVII International Conference on Interconnections between Particle Physics and Cosmology

Inflationary Gravitational Wave Spectral Shapes as test for Low-Scale Leptogenesis

16 Oct 2024, 18:30

15m

Auditorium 1, Convention Center (IIT Hyderabad)

Parallel talk Parallel - ASP & GW

Speaker

Ms Lekhika Malhotra (Indian Institute of Technology Bombay)

Description

We study thermal and non-thermal resonant leptogenesis in a general setting where a heavy scalar $\varphi$ decays to right-handed neutrinos (RHNs) whose further out-of-equilibrium decay generates the required lepton asymmetry. Domination of the energy budget of the Universe by the $\varphi$ or the RHNs alters the evolution history of the primordial gravitational waves (PGW), of inflationary origin, which re-enter the horizon after inflation, modifying the spectral shape. The decays of $\varphi$ and RHNs release entropy into the early Universe while nearly degenerate RHNs facilitate low and intermediate scale leptogenesis. We show that depending on the coupling $y_R$ of $\varphi$ to radiation species, RHNs can achieve thermal abundance before decaying, which gives rise to thermal leptogenesis. A characteristic damping of the GW spectrum resulting in two knee-like features or one knee-like feature would provide evidence for low-scale thermal and non-thermal leptogenesis respectively. The resulting novel features compatible with observed baryon asymmetry are detectable by future experiments like LISA and ET. By estimating signal-to-noise ratio (SNR) for upcoming GW experiments, we investigate the effect of the scalar mass $M_{\varphi }$ and reheating temperature $T_{\varphi }$, which depends on the $\varphi -N$ Yukawa couplings $y_N$.

Presentation materials

PPC 2024_Lekhika.pdf