Flavor violating leptonic decays of $$\tau $$ τ and $$\mu $$ μ leptons in the Standard Model with massive neutrinos
Abstract We have revisited the computations of the flavor violating leptonic decays of the $$\tau $$ τ and $$\mu $$ μ leptons into three lighter charged leptons in the Standard Model with massive neutrinos. We were driven by a claimed unnaturally large branching ratio predicted for the $$\tau ^-\rig...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
SpringerOpen
2019-01-01
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| Series: | European Physical Journal C: Particles and Fields |
| Online Access: | http://link.springer.com/article/10.1140/epjc/s10052-019-6563-4 |
| Summary: | Abstract We have revisited the computations of the flavor violating leptonic decays of the $$\tau $$ τ and $$\mu $$ μ leptons into three lighter charged leptons in the Standard Model with massive neutrinos. We were driven by a claimed unnaturally large branching ratio predicted for the $$\tau ^-\rightarrow \mu ^- \ell ^+ \ell ^-$$ τ-→μ-ℓ+ℓ- ($$\ell =\mu , e$$ ℓ=μ,e ) decays (Pham, Eur Phys J C 8:513 1999), which was at odds with the corresponding predictions for the $$\mu ^-\rightarrow e^- e^-e^+$$ μ-→e-e-e+ processes (Petcov, Sov J Nucl Phys 25:340 1977). In contrast with the prediction in [17], our results are strongly suppressed and in good agreement with the approximation made in Ref. [15], where masses and momenta of the external particles were neglected in order to deal with the loop integrals. However -as a result of keeping external momenta and masses in the computation of the dominant penguin and box diagrams- we even find slightly smaller branching fractions. Therefore, we confirm that any future observation of such processes would be an unambiguous manifestation of new physics beyond the Standard Model. |
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| ISSN: | 1434-6044 1434-6052 |