Beyond Neutrino Mass: Observable $n$-$\overline{n}$ Oscillations in UV Complete Seesaw Models

Fuente: arXiv
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Main Authors: Dorsner, Ilja, Fajfer, Svjetlana, Saad, Shaikh
Format: Preprint
Published: 2025
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author Dorsner, Ilja
Fajfer, Svjetlana
Saad, Shaikh
author_facet Dorsner, Ilja
Fajfer, Svjetlana
Saad, Shaikh
contents Next-generation experiments, such as the Deep Underground Neutrino Experiment and the European Spallation Source, are set to improve sensitivity to neutron-antineutron oscillation, a direct probe of $ΔB = 2$ baryon number violation, with particularly significant gains expected at the latter. The discovery of such a rare $ΔB = 2$ process would indicate physics beyond the Standard Model and could point to specific unified theories that allow observable $n-\overline{n}$ transitions. We accordingly examine $n-\overline{n}$ oscillations within a unified framework that accounts for charged fermion masses and generates viable neutrino masses via the seesaw mechanism. More specifically, we show that $n-\overline{n}$ oscillations can arise from two specific topologies within two distinct $SU(5)$ scenarios. One topology requires a presence of two color-sextet scalars in the Type II seesaw framework, whereas the other involves a scalar sextet and a color-octet fermion in the Type III seesaw framework. While the former topology can be realized in the $SO(10)$/Pati-Salam frameworks, the latter finds a natural embedding in $SU(5)$, which constitutes one of the key novelties of our work. Remarkably enough, the same dynamics responsible for fermion masses also induces baryon number violation, thus linking $n-\overline{n}$ oscillations to the flavor structure of the theory. We show that, given a TeV-scale mass for one of the colored states, upcoming searches for such $ΔB = 2$ processes can probe for a presence of the other colored states with masses up to $10^{11}\,\mathrm{GeV}$, well beyond the reach of colliders. This positions $n-\overline{n}$ oscillations as a rare low-energy portal to grand unification and ultra-heavy new physics.
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id arxiv_https___arxiv_org_abs_2509_00145
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Beyond Neutrino Mass: Observable $n$-$\overline{n}$ Oscillations in UV Complete Seesaw Models
Dorsner, Ilja
Fajfer, Svjetlana
Saad, Shaikh
High Energy Physics - Phenomenology
Next-generation experiments, such as the Deep Underground Neutrino Experiment and the European Spallation Source, are set to improve sensitivity to neutron-antineutron oscillation, a direct probe of $ΔB = 2$ baryon number violation, with particularly significant gains expected at the latter. The discovery of such a rare $ΔB = 2$ process would indicate physics beyond the Standard Model and could point to specific unified theories that allow observable $n-\overline{n}$ transitions. We accordingly examine $n-\overline{n}$ oscillations within a unified framework that accounts for charged fermion masses and generates viable neutrino masses via the seesaw mechanism. More specifically, we show that $n-\overline{n}$ oscillations can arise from two specific topologies within two distinct $SU(5)$ scenarios. One topology requires a presence of two color-sextet scalars in the Type II seesaw framework, whereas the other involves a scalar sextet and a color-octet fermion in the Type III seesaw framework. While the former topology can be realized in the $SO(10)$/Pati-Salam frameworks, the latter finds a natural embedding in $SU(5)$, which constitutes one of the key novelties of our work. Remarkably enough, the same dynamics responsible for fermion masses also induces baryon number violation, thus linking $n-\overline{n}$ oscillations to the flavor structure of the theory. We show that, given a TeV-scale mass for one of the colored states, upcoming searches for such $ΔB = 2$ processes can probe for a presence of the other colored states with masses up to $10^{11}\,\mathrm{GeV}$, well beyond the reach of colliders. This positions $n-\overline{n}$ oscillations as a rare low-energy portal to grand unification and ultra-heavy new physics.
title Beyond Neutrino Mass: Observable $n$-$\overline{n}$ Oscillations in UV Complete Seesaw Models
topic High Energy Physics - Phenomenology
url https://arxiv.org/abs/2509.00145