Abstract
Abstract We derive bounds on the mixing between the Standard Model (“active”) neutrinos and their right-chiral (“sterile”) counterparts in the see-saw models, by combining neutrino oscillation data and results of direct experimental searches. We demonstrate that the mixing of sterile neutrinos with any active flavour can be significantly suppressed for the values of the angle θ 13 measured recently by Daya Bay and RENO experiments. We reinterpret the results of searches for sterile neutrinos by the PS191 and CHARM experiments, considering not only charged current but also neutral current-mediated decays, as applicable in the case of see-saw models. The resulting lower bounds on sterile neutrino lifetime are up to an order of magnitude stronger than previously discussed in the literature. Combination of these results with the upper bound on the lifetime coming from primordial nucleosynthesis rule out the possibility that two sterile neutrinos with the masses between 10 MeV and the pion mass are solely responsible for neutrino flavour oscillations. We discuss the implications of our results for the Neutrino Minimal Standard Model (the νMSM).
Highlights
To their Standard Model (SM) counterparts via the Yukawa interaction, providing the Dirac masses, Md, for neutrinos
The resulting lower bounds on sterile neutrino lifetime are up to an order of magnitude stronger than previously discussed in the literature. Combination of these results with the upper bound on the lifetime coming from primordial nucleosynthesis rule out the possibility that two sterile neutrinos with the masses between 10 MeV and the pion mass are solely responsible for neutrino flavour oscillations
For the models (2.2), the compilation of constraints on various combinations of activesterile mixing angles
Summary
The minimal way to add sterile neutrinos to the Standard Model is provided by the Type I see-saw model [7,8,9,10] (see [24,25,26,27] and refs. therein):. Where FαI are new Yukawa couplings, Φi is the SM Higgs doublet, Φi = ǫijΦ†j This model is renormalizable, has the same gauge symmetries as the Standard Model, and contains N additional Weyl fermions NI — sterile neutrinos (NIc being the charge-conjugate fermion, in the chiral representation of Dirac γ-matrices NIc = iγ2NI†). The νMSM model contains 3 sterile neutrinos, whose masses are roughly of the order of those of other leptons in the Standard Model Two of these particles (approximately degenerate in their mass) are responsible for baryogenesis and neutrino oscillations and the third one is playing the role of dark matter. We limit our analysis by Ms ≤ 2 GeV, as for the higher masses the existing experimental bounds do not probe the region of mixing angles, required to produce successful baryogenesis in the νMSM [31]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
