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Nucleon Decays into Light New Particles in Neutrino Detectors

Julian Heeck ^1,* and Ian M. Shoemaker ^2,†

¹Department of Physics, University of Virginia, Charlottesville, Virginia 22904, USA
²Center for Neutrino Physics, Department of Physics, Virginia Tech, Blacksburg, Virginia 24601, USA

^*Contact author: heeck@virginia.edu
^†Contact author: shoemaker@vt.edu

Phys. Rev. Lett. 135, 111804 – Published 11 September, 2025

DOI: https://doi.org/10.1103/cxvm-p412

Abstract

Proton and neutron decays into light new particles $X$ can drastically change the experimental signatures and benefit from the complementarity of large water-Cherenkov neutrino detectors such as Super- and Hyper-Kamiokande and tracking detectors such as JUNO and DUNE. The proton decays $p \to ℓ^{+} X$ and $p \to π^{+} X$ with $m_{X}$ near phase-space closure lead to charged particles below the Cherenkov threshold, rendering them practically invisible in Super- and Hyper-Kamiokande but not in JUNO and DUNE, which are therefore uniquely positioned for these baryon-number-violating signatures despite their smaller size. As an additional signature, such nucleon decays in the Earth can produce a sizable flux of $X$ particles in underground detectors. We present a simple model in which nucleons decay into sub-GeV sterile neutrinos that subsequently decay through active-sterile neutrino mixing, with a promisingly large number of events in Super-Kamiokande even in the seesaw-motivated parameter space.

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Phys. Rev. Lett. 135, 111804– Published 11 September, 2025

Vol. 135, Iss. 11 — 12 September 2025

Received 19 June 2025
Accepted 22 August 2025

DOI: https://doi.org/10.1103/cxvm-p412

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

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Nucleon Decays into Light New Particles in Neutrino Detectors

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References (55)

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