First Evidence of Solar Neutrino Interactions on C13

O'Keeffe, Helen (2025) First Evidence of Solar Neutrino Interactions on C13. Physical review letters, 135 (24): 241803. ISSN 1079-7114

Abstract

The SNO+ Collaboration reports the first evidence of 8B solar neutrinos interacting on 13C nuclei. The charged current interaction proceeds through 13C +→13N+− which is followed, with a 10 minute half life, by 13N →13C+++. The detection strategy is based on the delayed coincidence between the electron and the positron. Evidence for the charged current signal is presented with a significance of 4.2⁢. Using the natural abundance of 13C present in the scintillator, 5.7 metric tons of 13 C over 231 days of data were used in this analysis. The 5.6+3.0−2.3 observed events in the data set are consistent with the expectation of 4.7+0.6−1.3 events. This result is the second real-time measurement of CC interactions of 8B neutrinos with nuclei and constitutes the lowest energy observation of neutrino interactions on 13C generally. This enables the first direct measurement of the CC reaction to the ground state of 13N, yielding an average cross section of (16.1+8.5−6.7⁢(stat.)+1.6−2.7⁢(syst.))×10−43  cm2 over the relevant 8B solar neutrino energies.