Standard Neutrino Spectrum from B-8 Decay

We present a systematic evaluation of the shape of the neutrino energy spectrum produced by beta-decay of $^8$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 $^8$B$(\beta^+){}^8$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 $\pm3\sigma$ deviations. Solar neutrino experiments that are currently being developed will be able to measure the shape of the $^8$B neutrino spectrum above about 5 MeV. An observed distortion of the $^8$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 $A=37$ system to calculate the $^8$B neutrino absorption cross section on chlorine: $\sigma_{\rm Cl}=(1.14\pm0.11)\times10^{-42}$~cm$^2$ ($\pm3\sigma$ errors). The chlorine cross section is also given as a function of the neutrino energy. The $^8$B neutrino absorption cross section in gallium is $\sigma_{\rm Ga}=(2.46^{+2.1}_{-1.1})\times10^{-42}$ cm$^2$ ($\pm3\sigma$ errors).Comment: Revised version, to appear in Phys. Rev.

On the Mass Eigenstate Purity of B^8 Solar Neutrinos

We give a brief report on our recent paper, hep-ph/0601198, in which we calculate the nu_2 mass eigenstate purity of B^8 solar neutrinos as 91 +/- 2 %.Comment: 3 pages, 2 postscript figures, latex, AIP conference style. PANIC 2005 proceeding

Effects of B-8 size on the low-energy Be7(p,gamma)B8 cross section

We calculate several "size-like" B-8 observables within the microscopic three-cluster model and study their potential constraints on the zero-energy astrophysical S_{17}(0) factor of the Be7(p,gamma)B8 reaction. We find within our three-cluster model that a simultaneous reproduction of the experimental data for the B-8 radius and quadrupole moment and of the B8-Li8 Coulomb displacement energy implies S_{17}(0)=(23-25) eVb.Comment: 8 pages with 1 figure. The original version with further details and more information are available at http://qmc.lanl.gov/~csot