Letter
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Nucleon decays into one lepton plus two nonstrange mesons

Wei-Qi Fan^1,2,3, Yi Liao ^1,2,*, and Xiao-Dong Ma ^1,2,†

¹State Key Laboratory of Nuclear Physics and Technology, Institute of Quantum Matter, South China Normal University, Guangzhou 510006, China
²Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter, Guangdong Provincial Key Laboratory of Nuclear Science, Guangzhou 510006, China
³School of Physics, Nankai University, Tianjin 300071, China

^*Contact author: liaoy@m.scnu.edu.cn
^†Contact author: maxid@scnu.edu.cn

Phys. Rev. D 114, L051701 – Published 29 September, 2026

DOI: https://doi.org/10.1103/96pd-vbhy

Abstract

Nucleon decays into a lepton and two pseudoscalar mesons represent key channels for probing baryon number violation, complementing conventional two-body modes. In this paper, we model-independently correlate two- and three-body processes within the framework of low-energy effective field theory, performing a global analysis that avoids single-operator-dominance assumption. We derive significantly improved bounds on 15 three-body modes with a lepton ( $e^{+}, μ^{+}, \hat{ν} = ν / \bar{ν}$ ) and two nonstrange mesons ( $π$ , $η$ ). For charged-lepton modes, our indirect lower limits on the partial lifetimes ( $Γ^{- 1}$ ) are more stringent than current Particle Data Group (PDG) values by more than three orders of magnitude. For five (anti)neutrino modes, we establish for the first time $Γ^{- 1} ≳ 10^{34} yr$ . Additionally, our analysis improves constraints on two-body processes $n \to e^{+} π^{-}$ , $n \to μ^{+} π^{-}$ , and $p \to \hat{ν} π^{+}$ by approximately a factor of 2 compared to the PDG limits. These results highlight the importance of leveraging correlations among different processes to better probe new physics, enabling more stringent constraints on experimentally challenging processes from well-measured ones.

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Phys. Rev. D 114, L051701– Published 29 September, 2026

Vol. 114, Iss. 5 — 1 September 2026

Received 2 May 2026
Accepted 4 September 2026

DOI: https://doi.org/10.1103/96pd-vbhy

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 one lepton plus two nonstrange mesons

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