Neutral-current reactions of solar and supernova neutrinos on deuterium

Abstract

We calculate the cross sections for the neutral-current disintegration of deuterium by neutrinos and antineutrinos: ν+d→ν’+n+p and ν¯+d→ν¯’+n+p. We put special emphasis on estimates of the theoretical uncertainties of these cross sections. For ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ and hep solar neutrinos, the averaged cross sections are 〈σ${(}^8$B)〉=4.1(1±0.1)×${10}^{\mathrm{-}43}$ ${\mathrm{cm}}^2$ and 〈σ(hep)〉=1.15(1±0.1)×${10}^{\mathrm{-}42}$ ${\mathrm{cm}}^2$, respectively, where hep denotes ${}_{}{}^3{}_{}{}^{}$He+p. The cross-section uncertainty is negligible, ±1/2%, for the ratio of neutral-current to charged-current events. Independent of neutrino oscillations, the cross sections correspond to 4.5(1±0.38)×${10}^3$ solar-neutrino events per year in the proposed one-kiloton Sudbury Neutrino Observatory if the standard solar model is correct. For a galactic supernova, the total number of neutral-current events expected in the Sudbury detector is about ${10}^3$ (distance/8 kpc${)}^{\mathrm{-}2}$; most of the signal is expected to arise from μ and τ neutrinos and antineutrinos. If either μ or τ neutrinos have a mass greater than 2×${10}^2$ eV, then this mass should be measurable using the neutrino signal from a galactic supernova.