Universal Seesaw Leptogenesis
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866909973909340160 |
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| author | Babu, K. S. Berbig, Maximilian Goswami, Srubabati Vatsyayan, Drona |
| author_facet | Babu, K. S. Berbig, Maximilian Goswami, Srubabati Vatsyayan, Drona |
| contents | We study the implications for leptogenesis in a class of left-right symmetric model, where all fermion masses are induced through the Universal Seesaw mechanism. Unlike conventional analyses, we do not use the decays of the neutrino embedded in the right-chiral lepton doublet, but rather those of the gauge-singlet mediators required for neutrino mass generation in the canonical Type-I seesaw. Due to the generalized parity symmetry that doubles the fermionic degrees of freedom in this model, we can generate the required $CP$ violation in the heavy fermion decays with only a single generation of mediators. One of the distinct features of our scenario is that the bounds from thermalization or washout via gauge interactions typically encountered in the canonical left-right symmetric models do not apply here. Moreover, the heavy mediators can decay to both the left and the right-chiral neutrinos, leading to a cancellation in the resulting baryon asymmetry for decays above the left-right symmetry breaking scale. We discuss ways to avoid this cancellation and show that low scale left-right symmetry breaking above the current collider limits is viable. The right chiral neutrinos also obtain their masses from the seesaw mechanism, and the lightest one turns out to have a sub-eV scale mass. We find that its abundance is consistent with standard cosmology, and it acts as potentially observable dark radiation. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_19833 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Universal Seesaw Leptogenesis Babu, K. S. Berbig, Maximilian Goswami, Srubabati Vatsyayan, Drona High Energy Physics - Phenomenology We study the implications for leptogenesis in a class of left-right symmetric model, where all fermion masses are induced through the Universal Seesaw mechanism. Unlike conventional analyses, we do not use the decays of the neutrino embedded in the right-chiral lepton doublet, but rather those of the gauge-singlet mediators required for neutrino mass generation in the canonical Type-I seesaw. Due to the generalized parity symmetry that doubles the fermionic degrees of freedom in this model, we can generate the required $CP$ violation in the heavy fermion decays with only a single generation of mediators. One of the distinct features of our scenario is that the bounds from thermalization or washout via gauge interactions typically encountered in the canonical left-right symmetric models do not apply here. Moreover, the heavy mediators can decay to both the left and the right-chiral neutrinos, leading to a cancellation in the resulting baryon asymmetry for decays above the left-right symmetry breaking scale. We discuss ways to avoid this cancellation and show that low scale left-right symmetry breaking above the current collider limits is viable. The right chiral neutrinos also obtain their masses from the seesaw mechanism, and the lightest one turns out to have a sub-eV scale mass. We find that its abundance is consistent with standard cosmology, and it acts as potentially observable dark radiation. |
| title | Universal Seesaw Leptogenesis |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2512.19833 |