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Title: The {sup 8}B neutrino spectrum

Abstract

Knowledge of the energy spectrum of {sup 8}B neutrinos is important for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed {beta}-decay approximation because of the broad {alpha}-unstable {sup 8}Be final state and recoil order corrections. We have measured the total energy of the {alpha} particles emitted following the {beta} decay of {sup 8}B. The measured {alpha} spectrum is inconsistent with a recent measurement of comparable precision. The {alpha} spectrum is fit using the R-matrix approach, which gives a functional form for the {beta}-decay strength function for the transition from {sup 8}B to the accessible excitation energies in {sup 8}Be. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments.

Authors:
 [1];  [2]; ;  [3]
  1. Nuclear Science Division, Lawrence Berkeley National Laboratory, California 94720 (United States)
  2. Physics Department, University of California, Berkeley, California 94720 (United States)
  3. Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
Publication Date:
OSTI Identifier:
20771297
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. C, Nuclear Physics; Journal Volume: 73; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevC.73.025503; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; ALPHA DECAY; ALPHA PARTICLES; ALPHA SPECTRA; APPROXIMATIONS; BERYLLIUM 8; BETA DECAY; BORON 8; CORRECTIONS; COSMIC NEUTRINOS; ENERGY SPECTRA; EXCITATION; ION EMISSION; POSITRONS; R MATRIX; RECOILS; SOLAR NEUTRINOS; STRENGTH FUNCTIONS

Citation Formats

Winter, W.T., Freedman, S.J., Rehm, K.E., and Schiffer, J.P.. The {sup 8}B neutrino spectrum. United States: N. p., 2006. Web. doi:10.1103/PhysRevC.73.025503.
Winter, W.T., Freedman, S.J., Rehm, K.E., & Schiffer, J.P.. The {sup 8}B neutrino spectrum. United States. doi:10.1103/PhysRevC.73.025503.
Winter, W.T., Freedman, S.J., Rehm, K.E., and Schiffer, J.P.. Wed . "The {sup 8}B neutrino spectrum". United States. doi:10.1103/PhysRevC.73.025503.
@article{osti_20771297,
title = {The {sup 8}B neutrino spectrum},
author = {Winter, W.T. and Freedman, S.J. and Rehm, K.E. and Schiffer, J.P.},
abstractNote = {Knowledge of the energy spectrum of {sup 8}B neutrinos is important for interpreting experiments that detect energetic neutrinos from the Sun. The neutrino spectrum deviates from the allowed {beta}-decay approximation because of the broad {alpha}-unstable {sup 8}Be final state and recoil order corrections. We have measured the total energy of the {alpha} particles emitted following the {beta} decay of {sup 8}B. The measured {alpha} spectrum is inconsistent with a recent measurement of comparable precision. The {alpha} spectrum is fit using the R-matrix approach, which gives a functional form for the {beta}-decay strength function for the transition from {sup 8}B to the accessible excitation energies in {sup 8}Be. Both the positron and neutrino energy spectra, corrected for recoil order effects, are constructed from the strength function. The positron spectrum is in good agreement with a previous direct measurement. The neutrino spectrum disagrees with previous experiments.},
doi = {10.1103/PhysRevC.73.025503},
journal = {Physical Review. C, Nuclear Physics},
number = 2,
volume = 73,
place = {United States},
year = {Wed Feb 15 00:00:00 EST 2006},
month = {Wed Feb 15 00:00:00 EST 2006}
}
  • We present a systematic evaluation of the shape of the neutrino energy spectrum produced by beta decay of {sup 8}B. We place special emphasis on determining the range of uncertainties permitted by existing laboratory data and theoretical ingredients (such as forbidden and radiative corrections). We review and compare the available experimental data on the {sup 8}B({beta}{sup +}){sup 8}Be(2{alpha}) decay chain. We analyze the theoretical and experimental uncertainties quantitatively. We give a numerical representation of the best-fit (standard-model) neutrino spectrum, as well as two extreme deviations from the standard spectrum that represent the total (experimental and theoretical) effective {plus_minus}3{sigma} deviations. Solarmore » neutrino experiments that are currently being developed will be able to measure the shape of the {sup 8}B neutrino spectrum above about 5 MeV. An observed distortion of the {sup 8}B solar neutrino spectrum outside the range given in the present work could be considered as evidence, at an effective significance level greater than three standard deviations, for physics beyond the standard electroweak model. We use the most recent available experimental data on the Gamow-Teller strengths in the {ital A}=37 system to calculate the {sup 8}B neutrino absorption cross section on chlorine: {sigma}{sub Cl}=(1.14{plus_minus}0.11){times}10{sup {minus}42} cm{sup 2} ({plus_minus}3{sigma} errors). The chlorine cross section is also given as a function of the neutrino energy. The {sup 8}B neutrino absorption cross section in gallium is {sigma}{sub Ga}=(2.46{sub {minus}1.1}{sup +2.1}){times}10{sup {minus}42} cm{sup 2} ({plus_minus}3{sigma} errors). {copyright} {ital 1996 The American Physical Society.}« less
  • No abstract prepared.
  • The Sudbury Neutrino Observatory (SNO) used an array of {sup 3}He proportional counters to measure the rate of neutral-current interactions in heavy water and precisely determined the total active ({nu}{sub x}) {sup 8}B solar neutrino flux. This technique is independent of previous methods employed by SNO. The total flux is found to be 5.54{sub -0.31}{sup +0.33}(stat){sub -0.34}{sup +0.36}(syst)x10{sup 6} cm{sup -2} s{sup -1}, in agreement with previous measurements and standard solar models. A global analysis of solar and reactor neutrino results yields {delta}m{sup 2}=7.59{sub -0.21}{sup +0.19}x10{sup -5} eV{sup 2} and {theta}=34.4{sub -1.2}{sup +1.3} degrees. The uncertainty on the mixing anglemore » has been reduced from SNO's previous results.« less
  • No abstract prepared.