First Evidence of Solar Neutrino Interactions on $^{13}$C
Authors:
SNO+ Collaboration,
:,
M. Abreu,
A. Allega,
M. R. Anderson,
S. Andringa,
D. M. Asner,
D. J. Auty,
A. Bacon,
T. Baltazar,
F. Barão,
N. Barros,
R. Bayes,
E. W. Beier,
A. Bialek,
S. D. Biller,
E. Caden,
M. Chen,
S. Cheng,
B. Cleveland,
D. Cookman,
J. Corning,
S. DeGraw,
R. Dehghani,
J. Deloye
, et al. (89 additional authors not shown)
Abstract:
The SNO+ Collaboration reports the first evidence of $^{8}\text{B}$ solar neutrinos interacting on $^{13}\text{C}$ nuclei. The charged current interaction proceeds through $^{13}\text{C} + ν_e \rightarrow {}^{13}\text{N} + e^-$ which is followed, with a 10 minute half-life, by ${}^{13}\text{N} \rightarrow {}^{13}\text{C} + e^+ +ν_e .$ The detection strategy is based on the delayed coincidence betw…
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The SNO+ Collaboration reports the first evidence of $^{8}\text{B}$ solar neutrinos interacting on $^{13}\text{C}$ nuclei. The charged current interaction proceeds through $^{13}\text{C} + ν_e \rightarrow {}^{13}\text{N} + e^-$ which is followed, with a 10 minute half-life, by ${}^{13}\text{N} \rightarrow {}^{13}\text{C} + e^+ +ν_e .$ 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$σ$. Using the natural abundance of $^{13}\text{C}$ present in the scintillator, 5.7 tonnes of $^{13}\text{C}$ 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 $^{8}\text{B}$ neutrinos with nuclei and constitutes the lowest energy observation of neutrino interactions on $^{13}\text{C}$ generally. This enables the first direct measurement of the CC $ν_e$ reaction to the ground state of ${}^{13}\text{N}$, yielding an average cross section of $(16.1 ^{+8.5}_{-6.7} (\text{stat.}) ^{+1.6}_{-2.7} (\text{syst.}) )\times 10^{-43}$ cm$^{2}$ over the relevant $^{8}\text{B}$ solar neutrino energies.
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Submitted 29 October, 2025; v1 submitted 28 August, 2025;
originally announced August 2025.