Constraints on lepton-flavor mixing with third-generation new physics
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arXiv
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| Auteurs principaux: | , , |
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| Format: | Preprint |
| Publié: |
2025
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| _version_ | 1866911740328935424 |
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| author | Covone, Sebastiano Morell, Pol Tinari, Arianna |
| author_facet | Covone, Sebastiano Morell, Pol Tinari, Arianna |
| contents | We study the implications of an approximate $U(2)^5$ flavor symmetry at the TeV scale, under the assumption of new physics predominantly coupled to the third-generation fermions, focusing on the breaking of the $U(2)_\ell$ subgroup governing the mixing between second- and third-generation left-handed leptons. We derive constraints on the corresponding spurion parameter $δ$ from current data on lepton flavor violating (LFV) and lepton flavor universality (LFU) observables, finding that $R_{K^{(*)}}$ and $\mathcal{B}(B_s \to μμ)$ give the most stringent bound on $δ$, yielding ${|δ|<0.051}$ at 95% CL. In addition, we provide updated bounds for LFV decay rates and discuss prospects for future sensitivity improvements, finding that future LFV searches could further tighten constraints on the mixing between second- and third-generation leptons. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2511_15800 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Constraints on lepton-flavor mixing with third-generation new physics Covone, Sebastiano Morell, Pol Tinari, Arianna High Energy Physics - Phenomenology We study the implications of an approximate $U(2)^5$ flavor symmetry at the TeV scale, under the assumption of new physics predominantly coupled to the third-generation fermions, focusing on the breaking of the $U(2)_\ell$ subgroup governing the mixing between second- and third-generation left-handed leptons. We derive constraints on the corresponding spurion parameter $δ$ from current data on lepton flavor violating (LFV) and lepton flavor universality (LFU) observables, finding that $R_{K^{(*)}}$ and $\mathcal{B}(B_s \to μμ)$ give the most stringent bound on $δ$, yielding ${|δ|<0.051}$ at 95% CL. In addition, we provide updated bounds for LFV decay rates and discuss prospects for future sensitivity improvements, finding that future LFV searches could further tighten constraints on the mixing between second- and third-generation leptons. |
| title | Constraints on lepton-flavor mixing with third-generation new physics |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2511.15800 |