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  • Letter
  • Open Access

Exploring leptogenesis in the era of first order electroweak phase transition

Dipendu Bhandari* and Arunansu Sil†

  • *Contact author: dbhandari@iitg.ac.in
  • †Contact author: asil@iitg.ac.in
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Phys. Rev. D 113, L091702 – Published 13 May, 2026

DOI: https://doi.org/10.1103/lp9n-97ns

Abstract

We present a novel approach for implementing baryogenesis via leptogenesis at low scale within the neutrino seesaw framework where a sufficient lepton asymmetry can be generated via out-of-equilibrium CP-violating decays of right-handed neutrinos (RHNs) even when their mass falls below the Standard Model (SM) Higgs mass. It becomes possible by keeping the sphaleron in equilibrium below its conventional decoupling temperature TspSM∼131.7  GeV in SM so as to facilitate the conversion of lepton asymmetry to baryon asymmetry at such a low scale, thanks to the flexibility of the bubble nucleation temperature in case the electroweak phase transition (EWPT) is of first order. The scenario emerges as an exciting (and perhaps unique) possibility for low scale leptogenesis, particularly if the Universe attains a reheating temperature lower than 131.7 GeV. We show that a stochastic gravitational wave, characteristic of such first order EWPT, may be detected in near future detectors, while the presence of RHNs of mass as low as 35 GeV opens up an intriguing detection possibility at current and future accelerator experiments.

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Phys. Rev. D 113, L091702– Published 13 May, 2026
  • Received 24 April 2025
  • Accepted 8 April 2026
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