Light sterile neutrinos

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.

Section: Jhep02(2016)083mentioning

confidence: 99%

“…The existence of sterile states is further motivated [16] JHEP02(2016)083 as they might provide an explanation to neutrino oscillation anomalies, or play a rôle in understanding several cosmological observations (being viable warm DM candidates, explaining pulsar velocities, etc. ).…”

Section: Sm Extensions Via Sterile Statesmentioning

confidence: 99%

Impact of sterile neutrinos on nuclear-assisted cLFV processes

Abada

Romeri

Teixeira

2016

“…In fact, a few anomalies have been recorded at the short baseline experiments, which cannot be accommodated in the 3-flavor scheme (see [6][7][8] for a review of the topic). The two standard mass-squared splittings ∆m 2 21 ≡ m 2 2 − m 2 1 and ∆m 2 31 ≡ m 2 3 − m 2 1 are too small to produce observable effects in such setups and (at least) one new much larger masssquared difference O(eV 2 ) must be introduced.…”

Section: Jhep02(2016)111mentioning

confidence: 99%

“…which the NOνA experiment aims to use during their full running time with a NuMI beam power of 700 kW and 120 GeV proton energy [56]. In our simulation, we assume that NOνA would also use 50% of its full exposure in the 8 Neutrinos at the Main Injector. neutrino mode which is 1.8 × 10 21 p.o.t.…”

Section: The Off-axis Experiments: T2k and Noνamentioning

confidence: 99%

Discovery potential of T2K and NOvA in the presence of a light sterile neutrino

Agarwalla

Chatterjee

Dasgupta

et al. 2016

Abstract:We study the impact of one light sterile neutrino on the prospective data expected to come from the two presently running long-baseline experiments T2K and NOνA when they will accumulate their full planned exposure. Introducing for the first time, the bi-probability representation in the 4-flavor framework, commonly used in the 3-flavor scenario, we present a detailed discussion of the behavior of the ν µ → ν e andν µ →ν e transition probabilities in the 3+1 scheme. We also perform a detailed sensitivity study of these two experiments (both in the stand-alone and combined modes) to assess their discovery reach in the presence of a light sterile neutrino. For realistic benchmark values of the mass-mixing parameters (as inferred from the existing global short-baseline fits), we find that the performance of both these experiments in claiming the discovery of the CP-violation induced by the standard CP-phase δ 13 ≡ δ, and the neutrino mass hierarchy get substantially deteriorated. The exact loss of sensitivity depends on the value of the unknown CP-phase δ 14 . Finally, we estimate the discovery potential of total CP-violation (i.e., induced simultaneously by the two CP-phases δ 13 and δ 14 ), and the capability of the two experiments of reconstructing the true values of such CP-phases. The typical (1σ level) uncertainties on the reconstructed phases are approximately 40 0 for δ 13 and 50 0 for δ 14 .

“…This disappearance is most likely due to active-sterile neutrino oscillations (see the review in ref. [10]). …”

Section: Introductionmentioning

confidence: 99%

Reactor fuel fraction information on the antineutrino anomaly

Giunti

Laveder

et al. 2017

Abstract:We analyzed the evolution data of the Daya Bay reactor neutrino experiment in terms of short-baseline active-sterile neutrino oscillations taking into account the theoretical uncertainties of the reactor antineutrino fluxes. We found that oscillations are disfavored at 2.6σ with respect to a suppression of the 235 U reactor antineutrino flux and at 2.5σ with respect to variations of the 235 U and 239 Pu fluxes. On the other hand, the analysis of the rates of the short-baseline reactor neutrino experiments favor active-sterile neutrino oscillations and disfavor the suppression of the 235 U flux at 3.1σ and variations of the 235 U and 239 Pu fluxes at 2.8σ. We also found that both the Daya Bay evolution data and the global rate data are well-fitted with composite hypotheses including variations of the 235 U or 239 Pu fluxes in addition to active-sterile neutrino oscillations. A combined analysis of the Daya Bay evolution data and the global rate data shows a slight preference for oscillations with respect to variations of the 235 U and 239 Pu fluxes. However, the best fits of the combined data are given by the composite models, with a preference for the model with an enhancement of the 239 Pu flux and relatively large oscillations.