Shape of the ⁸B Alpha and Neutrino Spectra

The β-delayed α spectrum from the decay of ⁸B has been measured with a setup that minimized systematic uncertainties that affected previous measurements. Consequently the deduced neutrino spectrum presents much smaller uncertainties than the previous recommendation [J. N. Bahcall et al., Phys. Rev. C 54, 411 (1996)]. The ⁸B ν spectrum is found to be harder than previously recommended with about (10–20)% more neutrinos at energies between 12–14 MeV. The integrated cross sections of the ³⁷Cl, ⁷¹Ga, ⁴⁰Ar, and Super-Kamiokande detectors are, respectively, 3.6%, 1.4%, 5.7%, and 2.1% larger than previously thought.