New avenues for $|\Delta B| = 2$ processes beyond neutron-antineutron oscillations

Bas i Beneito, Arnau (author), Fajfer, Svjetlana (author), Petrov, Alexey A. (author)

We explore baryon-number-violating $(|\Delta B| = 2)$ processes beyond the well-known neutron-antineutron $(n -\overline{n})$ oscillations, focusing on the $\Lambda - \overline{\Lambda}$ system. The presence of a strange quark in the $\Lambda$ 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 $(n -\overline{n})$ oscillations. Using the Standard Model Effective Field Theory (SMEFT), we classify all dimension-9 operators that cause $|\Delta B| = 2$ transitions and study their UV completions mediated by exotic scalar fields with trilinear interactions. We demonstrate that in these models, $\Lambda - \overline{\Lambda}$ oscillations can occur at tree level, with $(n -\overline{n})$ mixing potentially appearing at higher loop levels. We employ a chiral effective theory to constrain the effective mass mixing $\delta m_{\Lambda}$ , deriving bounds from current experimental limits on $(n -\overline{n})$ scillations and dinucleon decays such as $pp \rightarrow K^+K^+$. These bounds indicate that $\Lambda - \overline{\Lambda}$ oscillations probe a complementary parameter space, sensitive to baryon-number violation at scales up to $10^2 - 10^3$ TeV. We show that the existing indirect bounds make it challenging to provide a competitive bound on $\delta m_{\Delta}$ at BESIII.

• Language: English
• Keywords: physics of elementary particles, beyond the Standard Model, baryon number violation
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 34 str.
• Numbering: Vol. 2026, art. no. 124
• PID: 20.500.12556/RUL-180821
• UDC: 539.120
• ISSN on article: 1029-8479
• DOI: 10.1007/JHEP03(2026)124
• COBISS.SI-ID: 271796995
• Publication date in RUL: 17.03.2026

Record is a part of a journal

• Title: The journal of high energy physics
• Shortened title: J. high energy phys.
• Publisher: SISSA
• ISSN: 1029-8479
• COBISS.SI-ID: 1314148

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: fizika osnovnih delcev, fizika onkraj Standardnega modela, kršitev barionskega števila