New Avenues for |ΔB=2| Processes Beyond Neutron-Antineutron Oscillations

Author(s)

• Arnau Basi Beneito
• Svjetlana Fajfer
• Alexey A. Petrov, University of South CarolinaFollow

Document Type

Article

Abstract

We explore baryon-number-violating (|∆B| = 2) processes beyond the well-known neutron-antineutron (n-n̄) oscillations, focusing on the Λ-Λ̄ system. The presence of a strange quark in the Λ baryon introduces a new set of six-quark operators roughly of the form (uds)², which are different from the (udd)² operators responsible for n-n̄ oscillations. Using the Standard Model Effective Field Theory (SMEFT), we classify all dimension-9 operators that cause |∆B| = 2  transitions and study their UV completions mediated by exotic scalar fields with trilinear interactions. We demonstrate that in these models,  Λ-Λ̄ oscillations can occur at tree level, with n-n̄ mixing potentially appearing at higher loop levels. We employ a chiral effective theory to constrain the effective mass mixing δm&_Lambda;, deriving bounds from current experimental limits on n-n̄ oscillations and dinucleon decays such as pp → K⁺K⁺. These bounds indicate that Λ-Λ̄ oscillations probe a complementary parameter space, sensitive to baryon-number violation at scales up to 10² − 10³ TeV. We show that the existing indirect bounds make it challenging to provide a competitive bound on δm_Λ at BESIII.

Digital Object Identifier (DOI)

https://doi.org/10.1007/JHEP03(2026)124

Publication Info

Published in Journal of High Energy Physics, Volume 124, 2026.

© The Authors. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.

APA Citation

Beneito, A. B. i, Fajfer, S., & Petrov, A. A. (2026). New avenues for |∆B| = 2 processes beyond neutron-antineutron oscillations. Journal of High Energy Physics, 2026(3).https://doi.org/10.1007/JHEP03(2026)124