Neutrino oscillations: Present status and outlook

Abstract

Abstract. I summarize the status of three-flavour neutrino oscillations with date of Oct. 2007, and provide an outlook for the developments to be expected in the near future. Furthermore, I discuss the status of sterile neutrino oscillation interpretations of the LSND anomaly in the light of recent MiniBooNE results, and comment on implications for the future neutrino oscillation program.Keywords: Neutrino oscillations PACS: 14.60. Lm, 14.60.Pq, 14.60.St Thanks to the spectacular developments in neutrino oscillation experiments in the last years we have now a rough picture of the parameters governing three-flavour oscillations (see also Ref.[1] for an overview): There are two mass-squared differences separated roughly by a factor 30, there are two large mixing angles (θ 23 , which could even be 45 • , and θ 12 , which is large but smaller than 45 • at very high significance), and one mixing angle which has to be small (θ 13 ). Present data is consistent with two possibilities for the neutrino mass ordering, conventionally parametrized by the sign of ∆m 2 31 : In the normal ordering (∆m 2 31 > 0) the mass state which contains predominantly the electron neutrino has the smallest mass, whereas in the inverted ordering (∆m 2 31 < 0) it is part of a nearly degenerate doublet of mass states which is separated from the lightest neutrino mass by |∆m 2 31 |.

The interplay between GUT and flavour symmetries in a Pati-Salam × S4 model

“…For this reason also the terms with X (10) i must be taken into account, even if they are suppressed by an additional Λ. The other terms which are vanishing at this order of approximation are X (8) i for i = 4, 5, 6 and X (10) i for i = 6, . .…”

“…On the other hand it is a common belief that fermion mass and mixing matrix patterns can be explained by appealing to a flavour symmetry G f and in the last years particular attention has been devoted to the study of discrete flavour symmetries, thanks to their simplicity in recovering realistic lepton mixing patterns. The present neutrino oscillation data [1][2][3][4][5][6][7][8][9][10] are summarised in table 1, where we display the results of two independent global fits. The pattern of the mixings is characterised by two large angles and a small one: θ l 23 is compatible with a maximal value, but the accuracy admits relatively large deviations; θ l 12 is large, but about 5σ far from the maximal value; θ l 13 has only an upper bound.…”

T2K Long Baseline Neutrino Oscillation Experiment

“…•Improved measurement of sin 2 θ 23 via the ν μ disappearance search (current best fit from global data is 0.50 ± 0.13 at 2σ [2] ).…”

A measurement of hadron production cross sections for the simulation of accelerator neutrino beams and a search for muon-neutrino to electron-neutrino oscillations in the Δm² about equals 1-eV² region

“…In reality, however, there are subdominant effects and correlations between the three mixing and two mass-squared parameters. Global 3-ν fits of all oscillation data have been performed by various authors [40,41] and only their results will be summarized here. …”