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19–23 Dec 2024
Swatantrata Bhavan, Banaras Hindu University, Varanasi
Asia/Kolkata timezone

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

Not scheduled
20m
Swatantrata Bhavan, Banaras Hindu University, Varanasi

Swatantrata Bhavan, Banaras Hindu University, Varanasi

Department of Physics, I.Sc., Banaras Hindu University, 221005 Varanasi, India
Oral Astroparticle physics and cosmology

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 ϕ 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 ϕ 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 ϕ 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 yR of ϕ 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 knee-like features would provide evidence for low-scale thermal and non-thermal leptogenesis. We explore the parameter space for the lightest right-handed neutrino mass M1[102,1014] GeV and washout parameter K that depends on the light-heavy neutrino Yukawa couplings λ,
in the weak (K<1) and strong (K>1) washout regimes. 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 Mϕ and reheating temperature Tϕ, which depends on the ϕN Yukawa couplings yN.

Field of contribution Phenomenology

Authors

Anish Ghoshal (University of Warsaw, Poland) Ms Lekhika Malhotra (Indian Institute of Technology Bombay) Urjit Yajnik (IIT Bombay, Mumbai) Zafri Ahmed Borboruah (IIT Bombay)

Presentation materials

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