Abstract
We study lepton flavour violating two- and three-body decays of pseudoscalar mesons in Effective Field Theory (EFT). We give analytic formulae for the decay rates in the presence of a complete basis of QED and QCD-invariant operators. The constraints are obtained at the experimental scale, then translated to the weak scale via one-loop RGEs. The large RG-mixing between tensor and (pseudo)scalar operators weakens the constraints on scalar and pseudoscalar operators at the weak scale.
Highlights
The discovery of neutrino oscillations [1,2] established nonzero neutrino masses and mixing angles [3]
Another possibility is to look for new processes among known Standard Model (SM) particles, such as charged lepton flavor violation (CLFV) [6,7], which we define to be a contact interaction that changes the flavor of charged leptons
We found that tensor operators do not contribute to the leptonic decays but only to the semileptonic decays, in which the interference between εS;L and εTR vanishes
Summary
The discovery of neutrino oscillations [1,2] established nonzero neutrino masses and mixing angles [3]. We assume that these decays could be mediated by two-lepton, two-quark contact interactions, induced by heavy new particles at the scale ΛNP > mW. The constraints on combinations of lepton-flavorchanging operator coefficients, which can be obtained from the decays of same-flavor mesons, were studied in Ref. The aim of this paper is to obtain constraints on the operator coefficients describing meson decays at the experimental scale, and transport the bounds to the weak scale [59]. The operators describing the contact interactions that can mediate leptonic (qiqj → μe) and semileptonic (qi → qjμe) CLFV pseudoscalar meson decays at a scale Λexp ∼ 2 GeV (Λexp ∼ mb ≃ 4.2 GeV for bs and bd) are written as. We compute the branching ratio for the (semi)leptonic decays as a function of the coefficients of Eq (5)
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