ar X iv : h ep - p h / 98 09 20 6 v 1 1 S ep 1 99 8 ν μ ↔ ν τ vs ν μ ↔ ν s solutions for the atmospheric neutrino problem ∗
نویسنده
چکیده
Recent atmospheric neutrino data by Superkamiokande [1–3] provide strong evidence for neutrino oscillations. It has been shown [1–3] that atmospheric neutrino data favor νμ ↔ ντ oscillations with maximal mixing, rather than νμ ↔ νe. However, νμ disappearance alone does not imply uniquely a νμ ↔ ντ solution and there is another solution νμ ↔ νs, where νs denotes a sterile neutrino. In this talk some aspects of the νμ ↔ ντ and νμ ↔ νs solutions are discussed. In the past there has been a prejudice against the νμ ↔ νs solution to the atmospheric neutrino problem. The argument [4] was based on big bang nucleosynthesis which gives a condition ∆m sin 2θ< ∼ eV in order for sterile neutrinos not to be in thermal equilibrium. However, there was a loophole in this argument. Foot and Volkas [5] have shown that large lepton asymmetries will suppress νs ↔ νx neutrino oscillations. Interestingly, given certain conditions, the required lepton asymmetries can actually be created by the oscillations themselves [5]. So there is no longer any obstruction to νμ ↔ νs as a solution to the atmospheric neutrino anomaly. Many models [6,7] have been proposed which predict large or maximal active-sterile mixing. Among others, Foot and Volkas have been obsessed by exact parity symmetric models [7] and this was the main motivation of [8] in which νμ ↔ νs was examined in detail by fitting to the contained events of the Superkamiokande atmo-
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تاریخ انتشار 1998