Model discriminating power ofμ→econversion in nuclei

Abstract

We assess the model discriminating power of a combined phenomenological analysis of µ → eγ and µ → e conversion on different target nuclei, including the current hadronic uncertainties. We find that the theoretical uncertainties can be largely reduced by using input from lattice QCD and do not constitute a limiting factor in discriminating models where one or at most two underlying operators (dipole, scalar, vector) provide the dominant source of lepton flavor violation. Our results show that a realistic discrimination among underlying mechanisms requires a measurement of the ratio of conversion rates at the 5% level (two light nuclei) or at the 20% level (one light and one heavy nucleus). We have illustrated these main conclusions also in the context of a supersymmetric model.

Model-discriminating power of lepton flavor violatingτdecays

“…Detailed treatments of LFV µ − e transitions within an effective field theory (EFT) approach to NP have been performed in Refs. [36][37][38][39]. From these works it emerges that the nucleus-dependence of µ to e conversion rate is a powerful diagnosing tool, that extends the discriminating power of µ → eγ and µ → 3e [40] to operators involving quarks.…”

Lepton flavor-violating transitions in effective field theory and gluonic operators

“…The number of relevant operators in Eqs. (1) and (5) is reduced if one only considers coherent µ + N → e + N transitions 1 [3].…”

“…Interactions of flavor-changing neutral currents (FCNC) of leptons with hadrons, either in muon conversion or in tau or meson decays can be described in terms of effective operators of increasing dimension [3]. In order to set up an EFT calculation, however, one must first discuss the multitude of scales present in lepton FCNC transitions.…”

“…Studies of specific models in this framework are equivalent to specifying Wilson coefficients of effective operators. Second, EFT allows for studies of relative contributions of various operators and may even provide clues as to what experiments need to be done to discriminate among different possible models of new physics [3].…”

A Model of Neutrino Masses and Mixings and Its Phenomenological Implications

“…The most general CLFV effective Lagrangian which contributes to the µ−e conversion in nuclei has been studied by various groups [112,113,123]. At the scale Λ where the heavy particles (including particles beyond the SM as well as the heavy top, bottom and charm quarks) being integrated out, the relevant terms for the model we are studying are…”