Sterile neutrino oscillations: the global picture

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.

Section: Results: "3+1" Effective Modelmentioning

confidence: 99%

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

Abada

Romeri

Teixeira

2014

“…2 The analyses performed in [19,37] with the existing data from T2K and NOνA have already shown that these two experiments 3 can probe one of the new CP-phases for realistic values of the mixing angles indicated by the global 3+1 fits [42,43]. In addition, in [37] it has been pointed out that the statistical significance of the current indications concerning the standard CP-phase δ and the neutrino mass hierarchy is modified (reduced) in the presence of sterile neutrinos.…”

Section: Jhep02(2016)111mentioning

confidence: 92%

“…The first of the two interference terms is connected to the standard solar-atmospheric interference, while the second one is driven by the atmospheric-sterile interference. The conversion probability depends on the three small mixing angles θ 13 , θ 14 , θ 24 , whose best estimates, derived from the global 3-flavor (for θ 13 ) analyses [44][45][46] and from the 3+1 fits [42,43] where ∆ ≡ ∆m 2 31 L/4E is the atmospheric oscillating factor, which depends on the baseline L and the neutrino energy E. The two LBL experiments under consideration, T2K and NOνA, make use of an off-axis configuration, which leads to a narrow-band sharply-peaked energy spectrum of the emitted neutrinos. In theory, the off-axis angle should be tuned exactly to match (at the peak energy) the condition ∆ ∼ π/2, corresponding to the first oscillation maximum.…”

Section: Analytical Expressions In Vacuum and Mattermentioning

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 would imply that instead of the three-neutrino mixing scheme (in oscillation phenomena), one would have a 3 + 1-neutrino (or 3+more) mixing schemes (see, for instance, [33]). …”

Section: Jhep08(2016)079mentioning

confidence: 99%

Electron electric dipole moment in Inverse Seesaw models

Abada

Toma

2016

Abstract:We consider the contribution of sterile neutrinos to the electric dipole moment of charged leptons in the most minimal realisation of the Inverse Seesaw mechanism, in which the Standard Model is extended by two right-handed neutrinos and two sterile fermion states. Our study shows that the two pairs of (heavy) pseudo-Dirac mass eigenstates can give significant contributions to the electron electric dipole moment, lying close to future experimental sensitivity if their masses are above the electroweak scale. The major contribution comes from two-loop diagrams with pseudo-Dirac neutrino states running in the loops. In our analysis we further discuss the possibility of having a successful leptogenesis in this framework, compatible with a large electron electric dipole moment.