Solar neutrinos: Global analysis with day and night spectra from SNO

Abstract

We perform global analysis of the solar neutrino data including the day and night spectra of events at SNO. In the context of two active neutrino mixing, the best fit of the data is provided by the LMA MSW solution with ∆m 2 = 6.15 · 10 −5 eV 2 , tan 2 θ = 0.41, f B = 1.05, where f B is the boron neutrino flux in units of the corresponding flux in the Standard Solar Model (SSM). At 3σ level we find the following upper bounds: tan 2 θ < 0.84 and ∆m 2 < 3.6 · 10 −4 eV 2 . From 1σ-interval we expect the day-night asymmetries of the charged current and electron scattering events to be: A CC DN = 3.9 +3.6 −2.9 % and A ES DN = 2.1 +2.1 −1.4 %. The only other solution which appears at 3σ-level is the VAC solution with ∆m 2 = 4.5 · 10 −10 eV 2 , tan 2 θ = 2.1 and f B = 0.75. The best fit point in the LOW region, with ∆m 2 = 0.93 · 10 −7 eV 2 and tan 2 θ = 0.64, is accepted at 99.95% (3.5σ) C.L. . The least χ 2 point from the SMA solution region, with ∆m 2 = 4.6·10 −6 eV 2 and tan 2 θ = 5·10 −4 , could be accepted at 5.5σ-level only. In the three neutrino context the influence of θ 13 is studied. We find that with increase of θ 13 the LMA best fit point shifts to larger ∆m 2 , mixing angle is practically unchanged, and the quality of the fit becomes worse. The fits of LOW and SMA slightly improve. Predictions for KamLAND experiment (total rates, spectrum distortion) have been calculated.

LMA and sterile neutrinos: a case for resonance spin flavour precession

“…One of the generic predictions of LMA is an exceedingly large rate [7] for the Cl experiment [8]. This discrepancy reaches an excess of 2.5 σ if one uses the latest BP'04 results [9].…”

Synergies between the first-generation JHF-SK and NuMI superbeam experiments

“…Solar neutrinos also undergo flavor transitions [2,3] solving the long standing solar neutrino problem, even though the L/E dependence of oscillations is in this case not yet established. Oscillations are, however, by far the most plausible explanation and global fits to all available data clearly favor the so-called LMA solution for the mass splittings and mixings [4][5][6][7]. The CHOOZ reactor experiment [8] moreover currently provides the most stringent upper bound for the sub-leading U e3 element of the neutrino mixing matrix.…”

Solar neutrinos: What is next?

“…From the pre-salt analysis we had: (∆m 2 , tan 2 θ) = (6.15 · 10 −5 , 0.41) [21]. So, the SNO-II data only slightly shifted the best fit point to smaller values of ∆m 2 and tan 2 θ.…”

“…1. Details can be found in [19] and in our previous publications [20,21]. All the solar neutrino fluxes, but the boron neutrino flux, are taken according to SSM BP2000 [2].…”