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Freeze-in leptogenesis without the need for right-handed neutrino oscillations

Martin A. Mojahed1,* and Sascha Weber2,†

  • *Contact author: martin.mojahed@roma1.infn.it
  • †Contact author: wesascha@uni-mainz.de
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Phys. Rev. D 114, 015018 – Published 13 July, 2026

DOI: https://doi.org/10.1103/b7jy-1xh5

Abstract

We present an experimentally testable leptogenesis mechanism based on the standard type-I seesaw model that successfully operates at right-handed-neutrino (RHN) masses around the GeV scale. The mechanism takes place in a cosmological background with an asymmetry between right-handed electrons and left-handed positrons generated at high temperatures, and does not require oscillations between RHNs or any CP violation in the combined active-sterile neutrino sector. In contrast to standard leptogenesis via freeze-in, our mechanism works even in the presence of a single RHN around the GeV scale. The mechanism is illustrated for the minimal type-I seesaw with two RHNs, where we show that successful baryogenesis via leptogenesis is viable in large regions of parameter space even without a small mass splitting between the RHNs.

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Phys. Rev. D 114, 015018– Published 13 July, 2026
  • Received 14 January 2026
  • Accepted 10 June 2026
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