Solar neutrinos with magnetic moment: rates and global analysis

Abstract

A statistical analysis of the solar neutrino data is presented assuming the solar neutrino deficit to be resolved by the resonant interaction of the neutrino magnetic moment with the solar magnetic field. Four field profiles are investigated, all exhibiting a rapid increase across the bottom of the convective zone, one of them closely following the requirements from recent solar physics investigations. First a 'rates only' analysis is performed whose best fits appear to be remarkably better than all fits from oscillations. A global analysis then follows with the corresponding best fits of a comparable quality to the LMA one. Despite the fact that the resonant spin flavour precession does not predict any day/night effect, the separate SuperKamiokande day and night data are included in the analysis in order to allow for a direct comparison with oscillation scenarios. Remarkably enough, the best fit for rates and global analysis which is compatible with most astrophysical bounds on the neutrino magnetic moment is obtained from the profile which most closely follows solar physics requirements. Allowing for a peak field value of 3 × 10 5 G, it is found in this case that ∆m 2 21 = 1.46 × 10 −8 eV 2 , µ ν = 3.2 × 10 −12 µ B (64%CL). The new forthcoming experiments on solar neutrino physics (Kamland and Borexino) will be essential to ascertain whether this fact is incidental or essential. *

Low energy solar neutrinos and spin flavour precession

“…However, of these free parameters, the value of ∆m 2 10 is fixed from a joint optimization of Ga I and Ga II fits. We evaluate in each case the global χ 2 (rates + spectrum) referring the reader to [30] for definitions. Our objective then consists in finding appropriate solar field profiles for each of the Ga data sets together with the other solar data which provide the best possible fits.…”

Charge Radius and Effective Couplings via the v<sub>μ</sub>e<sup>-</sup>→ v<sub>μ</sub>e<sup>-</sup>

“…  , the second and third terms in (7) is zero and Equation (7) is reduced to the expressions (A. 5,17) given in Refs. [30,31]:…”

“…As a result, this has motivated vigorous efforts, both on the theoretical and experimental sides, to understand the detailed properties of neutrinos and of their interactions more in depth. In particular, electromagnetic properties of the neutrinos can play important roles in a wide variety of domains such as cosmology [14] and astrophysics [15,16], and can play a role in the deficit of electron neutrinos from the sum [17][18][19].…”

Light sterile neutrinos, spin flavour precession and the solar neutrino experiments

“…All event rates (total and spectral) were evaluated as described in refs. [32,33]. The expression for the 8 B spectral rate as applied to the SuperKamiokande and Borexino experiments with three active neutrinos is now 16) where σ e is the charged and neutral current cross section and σ µ,τ is the neutral current one.…”