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?Comment: Updated all calculations to include SNO salt-phase data and improved GNO and SAGE data, all released September 7, 2003 at TAUP03. Updating produces only minor numerical changes. Accepted for publication in JHE

Probing New Physics by Comparing Solar and KamLAND Data

We explore whether KamLAND and solar data may end up inconsistent when analyzed in terms of two-flavor neutrino oscillations. If this turned out to be the case, one would be led to conclude that there is more new physics, besides neutrino masses and mixing, in the leptonic sector. On the other hand, given that KamLAND and solar data currently agree when analyzed in terms of two-flavor neutrino oscillations, one is able to place nontrivial bounds on several manifestations of new physics. In particular, we compute how well a combined KamLAND and solar data analysis is able to constrain a specific form of violation of CPT invariance by placing a very stringent upper bound, |Delta m^2 - Delta bar{m}^2| < 1.1 10^{-4} eV^2 (3 sigma). We also estimate upper bounds on sin^2 theta - sin^2 bar{theta}. These are quite poor due to the fact that matter effects are almost irrelevant at KamLAND, which leads to an intrinsic inability to distinguish whether the antineutrino mixing angle is on the light (bar{theta} pi/4). We briefly discuss whether this ambiguity can be resolved by future long-baseline bar{nu}_e to bar{nu}_{e,mu} searches.Comment: Reference adde

Neutrino footprint in Large Scale Structure

Recent constrains on the sum of neutrino masses inferred by analyzing cosmological data, show that detecting a non-zero neutrino mass is within reach of forthcoming cosmological surveys, implying a direct determination of the absolute neutrino mass scale. The measurement relies on constraining the shape of the matter power spectrum below the neutrino free streaming scale: massive neutrinos erase power at these scales. Detection of a lack of small-scale power, however, could also be due to a host of other effects. It is therefore of paramount importance to validate neutrinos as the source of power suppression at small scales. We show that, independent on hierarchy, neutrinos always show a footprint on large, linear scales; the exact location and properties can be related to the measured power suppression (an astrophysical measurement) and atmospheric neutrinos mass splitting (a neutrino oscillation experiment measurement). This feature can not be easily mimicked by systematic uncertainties or modifications in the cosmological model. The measurement of such a feature, up to 1% relative change in the power spectrum, is a smoking gun for confirming the determination of the absolute neutrino mass scale from cosmological observations. It also demonstrates the synergy of astrophysics and particle physics experiments.Comment: arXiv admin note: text overlap with arXiv:1003.591

Solar neutrinos as probes of neutrino-matter interactions

Data from solar neutrino and KamLAND experiments have led to a discovery of nonzero neutrino masses. Here we investigate what these data can tell us about neutrino interactions with matter, including the poorly constrained flavor-changing nu_e-nu_tau interactions. We give examples of the interaction parameters that are excluded by the solar/KamLAND data and are beyond the reach of other experiments. We also demonstrate that flavor-changing interactions, at the allowed level, may profoundly modify the conversion probability for neutrinos of energy <~ 6 MeV and the values of the mass parameter inferred from the data. The implications for future experiments are discussed.Comment: 6 pages, 3 figure

Can we measure the neutrino mass hierarchy in the sky?

Cosmological probes are steadily reducing the total neutrino mass window, resulting in constraints on the neutrino-mass degeneracy as the most significant outcome. In this work we explore the discovery potential of cosmological probes to constrain the neutrino hierarchy, and point out some subtleties that could yield spurious claims of detection. This has an important implication for next generation of double beta decay experiments, that will be able to achieve a positive signal in the case of degenerate or inverted hierarchy of Majorana neutrinos. We find that cosmological experiments that nearly cover the whole sky could in principle distinguish the neutrino hierarchy by yielding 'substantial' evidence for one scenario over the another, via precise measurements of the shape of the matter power spectrum from large scale structure and weak gravitational lensing.Comment: Submitted to JCA

Solar neutrinos and the solar composition problem

Standard solar models (SSM) are facing nowadays a new puzzle: the solar composition problem. New determinations of solar metal abundances lead SSM calculations to conflict with helioseismological measurements, showing discrepancies that extend from the convection zone to the solar core and can not be easily assigned to deficiencies in the modelling of the solar convection zone. We present updated solar neutrino fluxes and uncertainties for two SSM with high (old) and low (new) solar metallicity determinations. The uncertainties in iron and carbon abundances are the largest contribution to the uncertainties of the solar neutrino fluxes. The uncertainty on the ^14N+p -> ^15O+g rate is the largest of the non-composition uncertainties to the CNO neutrino fluxes. We propose an independent method to help identify which SSM is the correct one. Present neutrino data can not distinguish the solar neutrino predictions of both models but ongoing measurements can help to solve the puzzle.Comment: 5 pages. To be submitte

Solar Neutrinos Before and After Neutrino 2004

We compare, using a three neutrino analysis, the allowed neutrino oscillation parameters and solar neutrino fluxes determined by the experimental data available Before and After Neutrino 2004. New data available after Neutrino2004 include refined KamLAND and gallium measurements. We use six different approaches to analyzing the KamLAND data. We present detailed results using all the available neutrino and anti-neutrino data for Delta m^2_{12}, tan^2 theta_{12}, sin^2 theta_{13}, and sin^2 eta (sterile fraction). Using the same complete data sets, we also present Before and After determinations of all the solar neutrino fluxes, which are treated as free parameters, an upper limit to the luminosity fraction associated with CNO neutrinos, and the predicted rate for a 7Be solar neutrino experiment. The 1 sigma (3 sigma) allowed range of Delta m^2_{21} = (8.2 +- 0.3) (^+1.0_-0.8)times 10^{-5} eV^2 is decreased by a factor of 1.7 (5), but the allowed ranges of all other neutrino oscillation parameters and neutrino fluxes are not significantly changed. Maximal mixing is disfavored at 5.8 sigma and the bound on the mixing angle theta_{13} is slightly improved to sin^2 theta_{13}<0.048 at 3 sigma. The predicted rate in a 7Be neutrino-electron scattering experiment is (0.665 +-0.015) of the rate implied by the BP04 solar model in the absence of neutrino oscillations. The corresponding predictions for p-p and pep experiments are, respectively, 0.707 {+0.011}{-0.013} and 0.644 {+0.011}{-0.013}. We derive upper limits to CPT violation in the weak sector by comparing reactor anti-neutrino oscillation parameters with neutrino oscillation parameters. We also show that the recent data disfavor at 91 % CL a proposed non-standard interaction description of solar neutrino oscillations.Comment: Added predictions for p-p and pep neutrino-electron scattering rate; publishe

Global Analysis of Solar Neutrino Oscillations Including SNO CC Measurement

For active and sterile neutrinos, we present the globally allowed solutions for two neutrino oscillations. We include the SNO CC measurement and all other relevant solar neutrino and reactor data. Five active neutrino oscillation solutions (LMA, LOW, SMA, VAC, and Just So2) are currently allowed at 3 sigma; three sterile neutrino solutions (Just So2, SMA, and VAC) are allowed at 3 sigma. The goodness of fit is satisfactory for all eight solutions. We also investigate the robustness of the allowed solutions by carrying out global analyses with and without: 1) imposing solar model constraints on the 8B neutrino flux, 2) including the Super-Kamiokande spectral energy distribution and day-night data, 3) including a continuous mixture of active and sterile neutrinos, 4) using an enhanced CC cross section for deuterium (due to radiative corrections), and 5) a optimistic, hypothetical reduction by a factor of three of the error of the SNO CC rate. For every analysis strategy used in this paper, the most favored solutions all involve large mixing angles: LMA, LOW, or VAC. The favored solutions are robust, but the presence at 3 sigma of individual sterile solutions and the active Just So2 solution is sensitive to the analysis assumptions.Comment: 9 figures, higher resolution versions at http://www.sns.ias.edu/~jnb, added references and clarification