Reanalysis of α+α scattering and the β-delayed α spectra from ⁸Li and ⁸B decays

We reanalyzed the Wilkinson-Alburger delayed-α spectra from ⁸Li and ⁸B decay, accounting for lepton-recoil broadening that had been neglected in previous analyses. This substantially improved the quality of the fits. The ⁸Li and ⁸B delayed-α spectra are now consistently described by the same ⁸Be final-state continuum. In our analysis, which did not invoke a low-lying intruder state, the discrepancy between the final-state continua inferred from the delayed-α spectra and from the L=2 α+α phase shifts is much less than found by previous authors. This largely resolves discrepancies noted by Barker and Warburton; the remaining differences may be artifacts of the assumption that the β-decay matrix elements are independent of excitation energy. Our analysis of the Wilkinson-Alburger data is consistent with results from the recent coincidence study of Ortiz et al., which gives additional confidence in using delayed-α spectra to infer the spectrum of ⁸B neutrinos that dominate the counting rate of many solar neutrino detectors.