New physics in multi-lepton tau decays
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arXiv
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| Main Authors: | , , , , , , |
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| Format: | Preprint |
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2026
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| _version_ | 1866910096618946560 |
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| author | Ema, Yohei Fox, Patrick J. Hostert, Matheus Menzo, Tony Pospelov, Maxim Ray, Anupam Zupan, Jure |
| author_facet | Ema, Yohei Fox, Patrick J. Hostert, Matheus Menzo, Tony Pospelov, Maxim Ray, Anupam Zupan, Jure |
| contents | Dark particles with lepton-flavor-violating couplings to the tau lepton can induce rare neutrinoless $τ$ decays with large final state multiplicities. We study models where transitions of the type $τ^\pm\to \ell^\pm\,ϕ$, with $ϕ$ a light new particle, initiate a chain of decays in the dark sector that terminate with decays into electrons, muons, or pions. These decay cascades appear as rare five or even seven-body $τ$ decays with multiple reconstructable resonances. We survey several representative models: kinetically mixed dark photon, gauged $L_i-L_j$ models, and other more exotic charge assignments such as chiral $U(1)'$ extensions of the Standard Model. The main new ingredient is the possibility of flavor violation at very high scales. In these models, a number of channels that have not yet been searched for experimentally, such as $τ\to 5μ$, $τ\to 3μ\,2e$, $τ\to μ\,4e$, and hadronic channels like $τ\to μ\,4π$, typically dominate over the previously-considered signatures such as $τ\to 3μ$. While some of the models, such as the gauged $L_i-L_j$ ones, also contain more challenging channels with missing energy due to decays to neutrinos, they can still be searched for via fully visible channels. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2604_01465 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | New physics in multi-lepton tau decays Ema, Yohei Fox, Patrick J. Hostert, Matheus Menzo, Tony Pospelov, Maxim Ray, Anupam Zupan, Jure High Energy Physics - Phenomenology High Energy Physics - Experiment Dark particles with lepton-flavor-violating couplings to the tau lepton can induce rare neutrinoless $τ$ decays with large final state multiplicities. We study models where transitions of the type $τ^\pm\to \ell^\pm\,ϕ$, with $ϕ$ a light new particle, initiate a chain of decays in the dark sector that terminate with decays into electrons, muons, or pions. These decay cascades appear as rare five or even seven-body $τ$ decays with multiple reconstructable resonances. We survey several representative models: kinetically mixed dark photon, gauged $L_i-L_j$ models, and other more exotic charge assignments such as chiral $U(1)'$ extensions of the Standard Model. The main new ingredient is the possibility of flavor violation at very high scales. In these models, a number of channels that have not yet been searched for experimentally, such as $τ\to 5μ$, $τ\to 3μ\,2e$, $τ\to μ\,4e$, and hadronic channels like $τ\to μ\,4π$, typically dominate over the previously-considered signatures such as $τ\to 3μ$. While some of the models, such as the gauged $L_i-L_j$ ones, also contain more challenging channels with missing energy due to decays to neutrinos, they can still be searched for via fully visible channels. |
| title | New physics in multi-lepton tau decays |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2604.01465 |