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 8 B solar neutrinos interacting on 13 C nuclei. The charged current interaction proceeds through 13 C +→13N+− which is followed, with a 10 minute half life, by 13 N →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 13 C 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 8 B neutrinos with nuclei and constitutes the lowest energy observation of neutrino interactions on 13 C generally. This enables the first direct measurement of the CC reaction to the ground state of 13 N , yielding an average cross section of (16.1+8.5 −6.7⁢(stat.)+1.6 −2.7⁢(syst.))×10−43  cm2 over the relevant 8 B solar neutrino energies.