What Fraction of Boron-8 Solar Neutrinos arrive at the Earth as a nu_2 mass eigenstate?

We calculate the fraction of B^8 solar neutrinos that arrive at the Earth as a nu_2 mass eigenstate as a function of the neutrino energy. Weighting this fraction with the B^8 neutrino energy spectrum and the energy dependence of the cross section for the charged current interaction on deuteron with a threshold on the kinetic energy of the recoil electrons of 5.5 MeV, we find that the integrated weighted fraction of nu_2's to be 91 \pm 2 % at the 95% CL. This energy weighting procedure corresponds to the charged current response of the Sudbury Neutrino Observatory (SNO). We have used SNO's current best fit values for the solar mass squared difference and the mixing angle, obtained by combining the data from all solar neutrino experiments and the reactor data from KamLAND. The uncertainty on the nu_2 fraction comes primarily from the uncertainty on the solar delta m^2 rather than from the uncertainty on the solar mixing angle or the Standard Solar Model. Similar results for the Super-Kamiokande experiment are also given. We extend this analysis to three neutrinos and discuss how to extract the modulus of the Maki-Nakagawa-Sakata mixing matrix element U_{e2} as well as place a lower bound on the electron number density in the solar B^8 neutrino production region.Comment: 23 pages, 8 postscript figures, latex. Dedicated to the memory of John Bahcall who championed solar neutrinos for many lonely year

Field-induced axion decay a→e+e−a \to e^+ e^- in KSVZ-model

The axion decay into electron-positron pair $a \to e^+ e^-$ is studied in an external magnetic field in KSVZ-model where axions have only induced coupling to leptons. The axion lifetime in the field decreases with energy and field strength to seconds.Comment: 4 pages, latex. Talk given at the International Workshop on Particle Physics and the Early Universe ``COSMO'97'', Ambleside, Lake District, England, 15-19 September 199

Comparison of slowness estimation methods according to borehole acoustic waveform data

© Copyright 2016.Methods for estimating the slowness of elastic waves according to a multi-element acoustic logging are discusses in the paper. Compare slowness curves of longitudinal and transverse waves for carbonate deposits is held. Interval times curves estimated by Semblance and dispersion methods have better convergence with each other. The reason for this is that these methods estimate the group velocity, as opposed to the hodograph method, which gives an estimate of the phase velocity. Convergence of slowness curves for the transverse wave is generally belter than convergence of curves for the longitudinal wave. All methods yield similar values slowness estimation errors

Analysis of excitation mechanisms of Ho³⁺ upconversion luminescence in Ho³⁺:LiYbF<inf>4</inf> (0.2 at %) crystal via photographs of its longitudinal cross sections and via spectral and kinetic characteristics

© 2016, Pleiades Publishing, Ltd.The results of a complex analysis of the excitation mechanisms of the up conversion luminescence of Ho3+:LiYbF4 (0.2 at %) crystal are presented. The spatial distribution of the upconversion luminescence intensity is studied by the photographs of longitudinal cross sections at different positions of the laser beam waist with respect to the sample. The surface power density of the pump laser diode radiation (0.755 W, λ = 933 nm) was changed by focusing the beam (similar to Z-scanning). The dependences of the longitudinal luminescence cross sections, as well as of the spectral and kinetic characteristics of Ho3+ and Yb3+ luminescence, on the position of the laser beam waist are determined. It is found that there exist two different mechanisms of the population of the energy levels of Ho3+ ions from which green and red luminescence occur, namely, cooperative sensitization of luminescence and absorption of induced photon groups (JETP Letters, 102 (5), 279 (2015)). It is shown that the contributions of these mechanisms vary both in time and over the crystal volume. All the observed spatial, spectral, and temporal specific features of the upconversion luminescence of Ho3+:LiYbF4 (0.2 at %) crystal are qualitatively explained

On the Evolution of the Neutrino State inside the Sun

We reexamine the conventional physical description of the neutrino evolution inside the Sun. We point out that the traditional resonance condition has physical meaning only in the limit of small values of the neutrino mixing angle, theta<<1. For large values of theta, the resonance condition specifies neither the point of the maximal violation of adiabaticity in the nonadiabatic case, nor the point where the flavor conversion occurs at the maximal rate in the adiabatic case. The corresponding correct conditions, valid for all values of theta including theta>pi/4, are presented. An adiabaticity condition valid for all values of theta is also described. The results of accurate numerical computations of the level jumping probability in the Sun are presented. These calculations cover a wide range of Delta m^2, from the vacuum oscillation region to the region where the standard exponential approximation is good. A convenient empirical parametrization of these results in terms of elementary functions is given. The matter effects in the so-called "quasi-vacuum oscillation regime" are discussed. Finally, it is shown how the known analytical results for the exponential, 1/x, and linear matter distributions can be simply obtained from the formula for the hyperbolic tangent profile. An explicit formula for the jumping probability for the distribution N_e ~ (coth(x/l) +- 1) is obtained.Comment: 34 pages, 8 figure

Neutrino Spectrum from SN 1987A and from Cosmic Supernovae

The detection of neutrinos from SN 1987A by the Kamiokande-II and Irvine-Michigan-Brookhaven detectors provided the first glimpse of core collapse in a supernova, complementing the optical observations and confirming our basic understanding of the mechanism behind the explosion. One long-standing puzzle is that, when fitted with thermal spectra, the two independent detections do not seem to agree with either each other or typical theoretical expectations. We assess the compatibility of the two data sets in a model-independent way and show that they can be reconciled if one avoids any bias on the neutrino spectrum stemming from theoretical conjecture. We reconstruct the neutrino spectrum from SN 1987A directly from the data through non-parametric inferential statistical methods and present predictions for the Diffuse Supernova Neutrino Background based on SN 1987A data. We show that this prediction cannot be too small (especially in the 10-18 MeV range), since the majority of the detected events from SN 1987 were above 18 MeV (including 6 events above 35 MeV), suggesting an imminent detection in operational and planned detectors.Comment: 9 pages, 4 figures; Matches version published in Phys. Rev.

Large Non-perturbative Effects of Small \Delta m^2_{21}/\Delta m^2_{31} and \sin \theta_{13} on Neutrino Oscillation and CP Violation in Matter

In the framework of three generations, we consider the CP violation in neutrino oscillation with matter effects. At first, we show that the non-perturbative effects of two small parameters, \Delta m_{21}^2/\Delta m_{31}^2 and \sin \theta_{13}, become more than 50% in certain ranges of energy and baseline length. This means that the non-perturbative effects should be considered in detailed analysis in the long baseline experiments. Next, we propose a method to include these effects in approximate formulas for oscillation probabilities. Assuming the two natural conditions, \theta_{23}=45^\circ and the fact that the matter density is symmetric, a set of approximate formulas, which involve the non-perturbative effects, has been derived in all channels.Comment: 25 pages, 4 figures, version to appear in JHE

Glassy Motion of Elastic Manifolds

We discuss the low-temperature dynamics of an elastic manifold driven through a random medium. For driving forces well below the $T=0$ depinning force, the medium advances via thermally activated hops over the energy barriers separating favorable metastable states. We show that the distribution of waiting times for these hopping processes scales as a power-law. This power-law distribution naturally yields a nonlinear glassy response for the driven medium, $v\sim\exp(-{\rm const}\times F^{-\mu})$.Comment: 4pages, revte

Detecting sterile dark matter in space

Space-based instruments provide new and, in some cases, unique opportunities to search for dark matter. In particular, if dark matter comprises sterile neutrinos, the x ray detection of their decay line is the most promising strategy for discovery. Sterile neutrinos with masses in the keV range could solve several long-standing astrophysical puzzles, from supernova asymmetries and the pulsar kicks to star formation, reionization, and baryogenesis. The best current limits on sterile neutrinos come from Chandra and XMM-Newton. Future advances can be achieved with a high-resolution x-ray spectrometry in space.Comment: 11 pages, 1 figure, to appear in proceedings "From Quantum to Cosmos: fundametal physics research in space", Washington, DC, May 22-24, 200