Shape of the B-8 alpha and neutrino spectra

The beta-delayed alpha spectrum from the decay of B-8 has been measured wit h a setup that minimized systematic uncertainties that affected previous me asurements; Consequently the deduced neutrino spectrum presents much smalle r uncertainties than the previous recommendation [J. N. Bahcall et al., Phy s. Rev. C 54, 411 (1996)]. The B-8 nu spectrum is found to be harder than p reviously recommended with about (10-20)% more neutrinos at energies betwee n 12-14 MeV. The integrated cross sections of the Cl-37, Ga-71, Ar-40, and Super-Kamiokande detectors are, respectively, 3.6%, 1.4%, 5.7%, and 2.1% la rger than previously thought.