The possibility off measuring for the first time neutrino-nuclei coherent scattering has been recently discussed by several experimental collaborations. It is shown that such a measurement may be very sensitive to non-standard interactions of neutrinos with quarks and might set better constraints than those coming from future neutrino factory experiments. We also comment on other types of new physics tests, such as extra heavy neutral gauge bosons, where the sensitivity to some models is slightly better than the Tevatron constraint and, therefore, could give complementary bounds.

The CERN Axion Solar Telescope (CAST) has extended its search for solar axions by using (3)He as a buffer gas. At T=1.8 K this allows for larger pressure settings and hence sensitivity to higher axion masses than our previous measurements with (4)He. With about 1 h of data taking at each of 252 different pressure settings we have scanned the axion mass range 0.39 eV≲m(a)≲0.64 eV. From the absence of excess x rays when the magnet was pointing to the Sun we set a typical upper limit on the axion-photon coupling of g(aγ)≲2.3×10(-10) GeV(-1) at 95% C.L., the exact value depending on the pressure setting. Kim-Shifman-Vainshtein-Zakharov axions are excluded at the upper end of our mass range, the first time ever for any solar axion search. In the future we will extend our search to m(a)≲1.15 eV, comfortably overlapping with cosmological hot dark matter bounds.

We study the sensitivity of future low energy neutrino experiments to extra neutral gauge bosons, leptoquarks and R-parity breaking interactions. We focus on future proposals to measure coherent neutrino-nuclei scattering and neutrino-electron elastic scattering. We introduce a new comparative analysis between these experiments and show that in different types of new physics it is possible to obtain competitive bounds to those of present and future collider experiments. For the cases of leptoquarks and R-parity breaking interactions we found that the expected sensitivity for most of the future low energy experimental setups is better than the current constraints.

Photons may convert into axion-like particles and back in the magnetic field of various astrophysical objects, including active galaxies, clusters of galaxies, intergalactic space and the Milky Way. This is a potential explanation for the candidate neutral ultra-high energy (E > 10 18 eV) particles from distant BL Lac type objects which probably have been observed by the High Resolution Fly's Eye experiment. Axions of the same mass and coupling may explain also TeV photons detected from distant blazars.

We re-analyse the resonant spin-flavour (RSF) solutions to the solar neutrino problem in the framework of analytic solutions to the solar magneto-hydrodynamics (MHD) equations. By substantially eliminating the arbitrariness associated to the magnetic field profile due to both mathematical consistency and physical requirements we propose the simplest scheme (MHD-RSF, for short) for solar neutrino conversion using realistic static MHD solutions. Using such effective twoparameter scheme we perform the first global fit of the recent solar neutrino data, including event rates as well as zenith angle distributions and recoil electron spectra induced by solar neutrino interactions in Superkamiokande. We compare quantitatively our simplest MHD-RSF fit with vacuum oscillation (VAC) and MSW-type (SMA, LMA and LOW) solutions to the solar neutrino problem using a common 1 E-mail: omr@fis.cinvestav.mx 2 E-mail: penya@flamenco.ific.uv.es 3 E-mail: rashba@izmiran.rssi.ru 4 E-mail: semikoz@flamenco.ific.uv.es 5 E-mail: valle@flamenco.ific.uv.es well-calibrated theoretical calculation and fit procedure. We find our MHD-RSF fit to be somewhat better than those obtained for the favored neutrino oscillation solutions, though not in a statistically significant way with ∆m 2 ≈ 10 −8 eV 2 and sin 2 2θ = 0. We briefly discuss the prospects to disentangle our MHD-RSF scenario from oscillation-type solutions to the solar neutrino problem at future solar neutrino experiments, giving some predictions for the SNO experiment.

We reexamine the sensitivity of solar neutrino oscillations to noise in the solar interior using the best current estimates of neutrino properties. Our results show that the measurement of neutrino properties at KamLAND provides new information about fluctuations in the solar environment on scales to which standard helioseismic constraints are largely insensitive. We also show how the determination of neutrino oscillation parameters from a combined fit of KamLAND and solar data depends strongly on the magnitude of solar density fluctuations. We argue that a resonance between helioseismic and Alfvén waves might provide a physical mechanism for generating these fluctuations, and, if so, neutrino oscillation measurements could be used to constrain the size of magnetic fields deep within the solar radiative zone.

A global analysis of spin-flavour precession (SFP) solutions to the solar neutrino problem is given, taking into account the impact of the full set of latest solar neutrino data, including the recent SNO data and the 1496-day Super-Kamiokande data. These are characterized by three effective parameters: ∆m 2 sol ≡ ∆m 2 , the neutrino mixing angle θ sol ≡ θ and the magnetic field parameter µB ⊥ . For the latter we adopt a self-consistent magneto-hydrodynamics field profile in the convective zone and identify an optimum B ⊥ ∼ 80 KGauss strength for µ = 10 −11 Bohr magneton. We find that no LOW-quasi-vacuum or vacuum solutions are present at 3 σ. In addition to the standard LMA oscillation solution, there are two SFP solutions, in the resonant (RSFP) and non-resonant (NRSFP) regimes. These two SFP solutions have goodness of fit 84 % (RSFP) and 83 % (NRSFP), slightly better than the LMA oscillation solution (78 %). We discuss the role of solar anti-neutrino searches in the fit and present a table of best-fit parameters and χ 2 min values. Should KamLAND confirm the LMA solution, the SFP solutions may at best be present at a sub-leading level, leading to a constraint on µB ⊥ . In the event LMA is not the solution realized in nature, then experiments such as Borexino can help distinguishing LMA from the NRSFP solution and the simplest RSFP solution with no mixing.In the appendix, we present an updated analysis combining the latest data from all solar neutrino experiments with the first results from KamLAND. We show that, although the SFP hypothesis still gives an excellent description of the solar data, it fails to account for the suppressed reactor neutrino flux detected at KamLAND. The inclusion of KamLAND excludes the SFP hypothesis at more than 3σ.

We discuss the impact of different solar neutrino data on the spin-flavor-precession (SFP) mechanism of neutrino conversion. We find that, although detailed solar rates and spectra allow the SFP solution as a subleading effect, the recent KamLAND constraint on the solar antineutrino flux places stronger constraints on this mechanism. Moreover, we show that for the case of random magnetic fields inside the Sun, one obtains a more stringent constraint on the neutrino magnetic moment down to the level of mu(nu)< or = few x 10(-12)mu(B), similar to bounds obtained from star cooling.