Precision measurement of the ratio of the charged kaon leptonic decay rates

Vicente

et al. 2014

113

107

Abstract:We address the impact of a modified W ℓν coupling on a wide range of observables, such as τ leptonic and mesonic decays, leptonic decays of pseudoscalar mesons, as well as semileptonic meson decays. In particular, we concentrate on deviations from lepton flavour universality, focusing on the ratios, and BR(B → τ ν). We further consider leptonic gauge boson decays, such as W → ℓν and Z → νν. For all the above observables, we provide the corresponding complete analytical expressions, derived for the case of massive neutrinos. Working in the framework of the Standard Model extended by additional sterile fermions, which mix with the active (left-handed) neutrinos, we numerically study the impact of active-sterile mixings on the above mentioned observables.

Section: Jhep02(2014)091supporting

confidence: 72%

Sterile neutrinos in leptonic and semileptonic decays

Vicente

et al. 2014

113

107

“…Further constraints arise from leptonic and semileptonic decays of pseudoscalar mesons K, D, D s , B (see [72,73] for kaon decays, [74,75] for D and D S decay rates, and [76,77] for B-meson observations). Recent studies suggest that in the framework of the SM extended by sterile neutrinos the most severe bounds arise from the violation of lepton universality in leptonic kaon decays (parametrised by the observable ∆r K ) [58,78].…”

Section: Jhep02(2016)083mentioning

confidence: 99%

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Romeri

2016

We discuss charged lepton flavour violating processes occurring in the presence of muonic atoms, such as muon-electron conversion in nuclei CR(µ − e, N), the (Coulomb enhanced) decay of muonic atoms into a pair of electrons BR(µ − e − → e − e − , N), as well as Muonium conversion and decay, Mu − Mu and Mu → e + e − . Any experimental signal of these observables calls for scenarios of physics beyond the Standard Model. In this work, we consider minimal extensions of the Standard Model via the addition of sterile fermions, providing the corresponding complete analytical expressions for all the considered observables. We first consider an "ad hoc" extension with a single sterile fermion state, and investigate its impact on the above observables. Two well motivated mechanisms of neutrino mass generation are then considered: the Inverse Seesaw embedded into the Standard Model, and the νMSM. Our study reveals that, depending on their mass range and on the active-sterile mixing angles, sterile neutrinos can give significant contributions to the above mentioned observables, some of them even lying within present and future sensitivity of dedicated cLFV experiments. We complete the analysis by confronting our results to other (direct and indirect) searches for sterile fermions.

“…Leptonic and semileptonic meson decays: further constraints arise from decays of pseudoscalar mesons K, D, D s and B, with one or two neutrinos in the final state (see [68,69] for kaon decays, [70,71] for D and D s decay rates, and [72,73] for B-meson observations). In the framework of the SM extended by sterile neutrinos, these decays have recently been addressed in [21,22].…”

Section: Jhep09(2014)074mentioning

confidence: 99%

Effect of steriles states on lepton magnetic moments and neutrinoless double beta decay

Romeri

2014

Abstract:We address the impact of sterile fermion states on the anomalous magnetic moment of charged leptons, as well as their contribution to neutrinoless double beta decays. We illustrate our results in a minimal, effective extension of the Standard Model by one sterile fermion state, and in a well-motivated framework of neutrino mass generation, embedding the Inverse Seesaw into the Standard Model. The simple "3+1" effective case succeeds in alleviating the tension related to the muon anomalous magnetic moment, albeit only at the 3σ level, and for light sterile states (corresponding to a cosmologically disfavoured regime). Interestingly, our analysis shows that a future 0ν2β observation does not necessarily imply an inverted hierarchy for the active neutrinos in this simple extension. Although the Inverse Seesaw realisation here addressed could indeed ease the tension in (g − 2) µ , bounds from lepton universality in kaon decays mostly preclude this from happening. However, these scenarios can also have a strong impact on the interpretation of a future 0ν2β signal regarding the hierarchy of the active neutrino mass spectrum.