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First Evidence of Solar Neutrino Interactions on $^{13}$C

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, M. M. Depatie, F. Di Lodovico, C. Dima, J. Dittmer, K. H. Dixon, M. S. Esmaeilian, E. Falk, N. Fatemighomi, R. Ford, A. Gaur, O. I. González-Reina, D. Gooding, C. Grant, J. Grove, S. Hall, A. L. Hallin, D. Hallman, M. R. Hebert, W. J. Heintzelman, R. L. Helmer, C. Hewitt, B. Hreljac, P. Huang, R. Hunt-Stokes, A. S. Inácio, C. J. Jillings, S. Kaluzienski, T. Kaptanoglu, J. Kladnik, J. R. Klein, L. L. Kormos, B. Krar, C. Kraus, C. B. Krauss, T. Kroupová, C. Lake, L. Lebanowski, C. Lefebvre, V. Lozza, M. Luo, S. Maguire, A. Maio, S. Manecki, J. Maneira, R. D. Martin, N. McCauley, A. B. McDonald, G. Milton, D. Morris, M. Mubasher, S. Naugle, L. J. Nolan, H. M. O'Keeffe, G. D. Orebi Gann, S. Ouyang, J. Page, S. Pal, K. Paleshi, W. Parker, L. J. Pickard, B. Quenallata, P. Ravi, A. Reichold, S. Riccetto, J. Rose, R. Rosero, J. Shen, J. Simms, P. Skensved, M. Smiley, R. Tafirout, B. Tam, J. Tseng, E. Vázquez-Jáuregui, J. G. C. Veinot, C. J. Virtue, F. Wang, M. Ward, J. J. Weigand, J. D. Wilson, J. R. Wilson, A. Wright, S. Yang, Z. Ye, M. Yeh, S. Yu, Y. Zhang, K. Zuber, A. Zummo

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 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.

First Evidence of Solar Neutrino Interactions on $^{13}$C

Abstract

The SNO+ Collaboration reports the first evidence of solar neutrinos interacting on nuclei. The charged current interaction proceeds through which is followed, with a 10 minute half-life, by 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 present in the scintillator, 5.7 tonnes of over 231 days of data were used in this analysis. The 5.6 observed events in the data set are consistent with the expectation of 4.7 events. This result is the second real-time measurement of CC interactions of neutrinos with nuclei and constitutes the lowest energy observation of neutrino interactions on generally. This enables the first direct measurement of the CC reaction to the ground state of , yielding an average cross section of cm over the relevant solar neutrino energies.

Paper Structure

This paper contains 1 equation, 4 figures, 1 table.

Figures (4)

  • Figure 1: The LR distribution for data (black) compared to the expected likelihood LR for the signal (blue) and background (red dashed).
  • Figure 2: Distribution of the difference in time $(\Delta T)$ and 3D position $(\Delta R)$ between the prompt and delayed events. Signal-like (LR $> 0$) events are shown as open blue circles and background-like (LR $< 0$) events as filled red circles.
  • Figure 3: The observed likelihood distribution for the $^{13}\text{C}$ interaction rate, compared to the expected rate. The theoretical prediction (shaded blue) agrees with the best fit signal rate of 1.6$^{+0.82}_{-0.65}$ ev/yr/tonne of $^{13}$C. The prediction rate only considering cross section uncertainty is shown in shaded black.
  • Figure 4: The SNO+ measured cross section for the $\nu$ + $^{13}$C CC reaction (black point) compared to the theoretical prediction Cross_Section_2012 for the ground state interaction (black line). Also shown is the previous KARMEN result KARMEN (red point) compared to the theoretical total cross section (red dashed). The theoretical cross section for the excited state interaction (blue dot-dash) is also shown. The horizontal error bars show the range of neutrino energies used for each measurement, with the data points placed in the centre of that range.