Low Energy Solar Neutrino Experiments Research Articles

Combined Effect of NSI and SFP on Solar Electron Neutrino Oscillation

The combined effect of spin-flavor precession (SFP) and the nonstandard neutrino interaction (NSI) on the survival probability of solar electron neutrinos (assumed to be Dirac particles) is examined for various values ofϵ11,ϵ12, andμB. It is found that the neutrino survival probability curves affected by SFP and NSI effects individually for some values of the parameters (ϵ11,ϵ12, andμB) get close to the standard MSW curve when both effects are combined. Therefore, the combined effect of SFP and NSI needs to be taken into account when the solar electron neutrino data obtained by low energy solar neutrino experiments is investigated.

Tagging radon daughters in low-energy scintillation detectors

One problematic source of background in scintillator-based low-energy solar neutrino experiments such as Borexino is the presence of radon gas and its daughters. The mean lifetime of the α -emitter 214 Po in the radon chain is sufficiently short, 0.24 ms, that its decay, together with that immediately preceding of 214 Bi, is easily recognized as a “coincidence event.” This fact, combined with the capability of α / β pulse-shape discrimination, makes it possible to tag decays of 222 Rn and its first four daughters via a likelihood-based method.

Constraining nonstandard interactions inνeeorν¯eescattering

We present a new analysis of non-universal and flavor changing non-standard neutrino interactions (NSI) in \nu_e e or \bar{\nu}_e e scattering. Our global analysis of these process includes all relevant experiments, such as the most recent MUNU measurement from reactor neutrinos, both in the context of the Standard Model as well as extensions where NSI are present. We also compare our constraints on non-universal and flavor changing NSI with results from previous analyses. We stress the importance of combining neutrino and anti-neutrino data in the resulting constraints on electroweak paramaters, and the important role that future low energy solar neutrino experiments can play in improving existing sensitivities.

A road map to solar neutrino fluxes, neutrino oscillation parameters, and tests for new physics

We analyze all available solar and related reactor neutrino experiments, as well as simulated future 7Be, p-p, pep, and ^8B solar neutrino experiments. We treat all solar neutrino fluxes as free parameters subject to the condition that the total luminosity represented by the neutrinos equals the observed solar luminosity (the `luminosity constraint'). Existing experiments show that the p-p solar neutrino flux is 1.02 +- 0.02 (1 sigma) times the flux predicted by the BP00 standard solar model; the 7Be neutrino flux is 0.93^{+0.25}_{-0.63} the predicted flux; and the ^8B flux is 1.01 +- 0.04 the predicted flux. The neutrino oscillation parameters are: Delta m^2 = 7.3^{+0.4}_{-0.6}\times 10^{-5} eV^2 and tan^2 theta_{12} = 0.41 +- 0.04. We evaluate how accurate future experiments must be to determine more precisely neutrino oscillation parameters and solar neutrino fluxes, and to elucidate the transition from vacuum-dominated to matter-dominated oscillations at low energies. A future 7Be nu-e scattering experiment accurate to +- 10 % can reduce the uncertainty in the experimentally determined 7Be neutrino flux by a factor of four and the uncertainty in the p-p neutrino flux by a factor of 2.5 (to +- 0.8 %). A future p-p experiment must be accurate to better than +- 3 % to shrink the uncertainty in tan^2 theta_{12} by more than 15 %. The idea that the Sun shines because of nuclear fusion reactions can be tested accurately by comparing the observed photon luminosity of the Sun with the luminosity inferred from measurements of solar neutrino fluxes. Based upon quantitative analyses of present and simulated future experiments, we answer the question: Why perform low-energy solar neutrino experiments?

Neutrino magnetic moments and low-energy solar neutrino-electron scattering experiments

The scattering of solar neutrinos on electrons is sensitive to the neutrino magnetic moments through an interference of electromagnetic and weak amplitudes in the cross section. We show that future low-energy solar neutrino experiments with good angular resolution can be sensitive to the resulting azimuthal asymmetries in event number and should provide useful information on non-standard neutrino properties such as magnetic moments. We compare asymmetries expected at Hellaz (mainly $\mathrm{pp}$ neutrinos) with those at the Kamiokande and Super-Kamiokande experiments (boron neutrinos), both for the case of Dirac and Majorana neutrinos and discuss the advantages of low energy experiments. Potentially interesting information on the solar magnetic fields may be accessible.