New Avenues for $|ΔB|$ = 2 Processes Beyond Neutron-Antineutron Oscillations
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| Format: | Preprint |
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2025
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| _version_ | 1866908637964795904 |
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| author | Beneito, Arnau Bas i Fajfer, Svjetlana Petrov, Alexey A. |
| author_facet | Beneito, Arnau Bas i Fajfer, Svjetlana Petrov, Alexey A. |
| contents | We explore baryon-number-violating ($|ΔB| = 2$) processes beyond the well-known neutron-antineutron ($n - \bar{n}$) oscillations, focusing on the $Λ- \bar Λ$ 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 $n - \bar{n}$ oscillations. Using the Standard Model Effective Field Theory (SMEFT), we classify all dimension-9 operators that cause $|ΔB|=2$ transitions and study their UV completions mediated by exotic scalar fields with trilinear interactions. We demonstrate that in these models, $Λ- \bar Λ$ oscillations can occur at tree level, with $n - \bar{n}$ mixing potentially appearing at higher loop levels. We employ a chiral effective theory to constrain the effective mass mixing $δm_Λ$, deriving bounds from current experimental limits on $n - \bar{n}$ oscillations and dinucleon decays such as $p \,p \to K^+ K^+$. These bounds indicate that $Λ- \barΛ$ 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 $δm_Λ$ at BESIII. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2511_05657 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | New Avenues for $|ΔB|$ = 2 Processes Beyond Neutron-Antineutron Oscillations Beneito, Arnau Bas i Fajfer, Svjetlana Petrov, Alexey A. High Energy Physics - Phenomenology We explore baryon-number-violating ($|ΔB| = 2$) processes beyond the well-known neutron-antineutron ($n - \bar{n}$) oscillations, focusing on the $Λ- \bar Λ$ 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 $n - \bar{n}$ oscillations. Using the Standard Model Effective Field Theory (SMEFT), we classify all dimension-9 operators that cause $|ΔB|=2$ transitions and study their UV completions mediated by exotic scalar fields with trilinear interactions. We demonstrate that in these models, $Λ- \bar Λ$ oscillations can occur at tree level, with $n - \bar{n}$ mixing potentially appearing at higher loop levels. We employ a chiral effective theory to constrain the effective mass mixing $δm_Λ$, deriving bounds from current experimental limits on $n - \bar{n}$ oscillations and dinucleon decays such as $p \,p \to K^+ K^+$. These bounds indicate that $Λ- \barΛ$ 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 $δm_Λ$ at BESIII. |
| title | New Avenues for $|ΔB|$ = 2 Processes Beyond Neutron-Antineutron Oscillations |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2511.05657 |