(3+1)-spectrum of neutrino masses: A chance for LSND?

Abstract

If active to active neutrino transitions are dominant modes of the atmospheric (ν µ → ν τ ) and the solar neutrino oscillations (ν e → ν µ /ν τ ), as is indicated by recent data, the favoured scheme which accommodates the LSND result -the so called (2+2)scheme -should be discarded. We introduce the parameters η atm s and η sun s which quantify an involvement of the sterile component in the solar and atmospheric neutrino oscillations. The (2+2)-scheme predicts η atm s +η sun s= 1 and the experimental proof of deviation from this equality will discriminate the scheme. In this connection the (3+1)scheme is revisited in which the fourth (predominantly sterile) neutrino is isolated from a block of three flavour neutrinos by the mass gap ∆m 2 LSN D ∼ (0.4 − 10) eV 2 . We find that in the (3 + 1)-scheme the LSND result can be reconciled with existing bounds on ν e -and ν µ -disappearance at 95−99% C.L.. The generic prediction of the scheme is the ν e -and ν µ -disappearance probabilities at the level of present experimental bounds.The possibility to strengthen the bound on ν µ -disappearance in the KEK -front detector experiment is studied. We consider phenomenology of the (3 + 1)-scheme, in particular, its implications for the atmospheric neutrinos, neutrinoless double beta decay searches, supernova neutrinos and primordial nucleosynthesis.

Sterile neutrino oscillations: the global picture

“…Limits on the mixing of ν τ with eV-scale states are obtained from data involving information from NC interactions, which allow to distinguish between 5 The relevant data samples are atmospheric and solar neutrinos (via the NC matter effect) and MINOS NC data. Furthermore, the parameter |U τ 4 | controls the relative weight of the oscillation modes ν µ → ν τ and ν µ → ν s at the "atmospheric" scale ∆m 2 31 : a large value of |U τ 4 | implies a large fraction of ν µ → ν s oscillations at the ∆m 2 31 scale. The limit in the plane of |U τ 4 | 2 and ∆m 2 41 is shown in the right panel of Fig.…”

Testing nonstandard neutrino properties with a Mössbauer oscillation experiment

“…See ref. [61][62][63][64][65][66][67] for a partial list of works that studied this possibility. In this model, the mixing between 4 neutrinos (3 active and 1 sterile) is described by six mixing angles and 3 CP phases.…”

Fabrication of Short-Range Ordered Nanoholes on Silicon Surfaces by Electron Irradiation

“…(See also [28,29].) 3 Although ref. [30] found support for chaoticity, their conclusion is not firm because of the reported loss of the numerical accuracy of their methods when approaching the potentially chaotic region.…”

“…However, while pure active-sterile solutions are disfavoured, sizable admixtures of sterile states in the observed fluxes are still allowed [3,4]. New sterile states are also needed in order to explain the LSND anomaly [5] by neutrino physics.…”

“…[26] is now discredited [27], it still remains true that no numerically reliable momentum dependent analysis has so far shown the existence of the chaotic region. 3 It is important to settle the issue because, as mentioned above, large L νe could significantly alter the helium-4 abundance. Indeed, if the sign of L νe were found to be chaotic, then Y He could not be reliably determined from BBN [18].…”