Flavor violating leptonic decays of τ and μ leptons in the Standard Model with massive neutrinos
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Hernández-Tomé, G., Castro, G. L., & Roig, P. (2019). Flavor violating leptonic decays of τ and μ leptons in the Standard Model with massive neutrinos. The European Physical Journal C, 79(1), 84.
SponsorshipFinally, we also acknowledge support from Conacyt through projects FOINS-296-2016 (Fronteras de la Ciencia), and 236394 and 250628 (Ciencia Básica).
We have revisited the computations of the flavor violating leptonic decays of the τ and 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 τ − → μ − l + l − (l = μ, e) decays (Pham, Eur Phys J C 8:513 1999), which was at odds with the corresponding predictions for the μ − → e−e−e+ processes (Petcov, Sov J Nucl Phys 25:340 1977). In contrast with the prediction in , our results are strongly suppressed and in good agreement with the approximationmade in Ref. , 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.