Improved Measurement of Solar Neutrinos from the Carbon-Nitrogen-Oxygen Cycle by Borexino and Its Implications for the Standard Solar Model
S. Appel, Z. Bagdasarian, D. Basilico, G. Bellini, J. Benziger, R. Biondi, B. Caccianiga, F. Calaprice, A. Caminata, P. Cavalcante, A. Chepurnov, D. D’Angelo, A. Derbin, A. Di Giacinto, V. Di Marcello, Xuefeng Ding, A. Di Lüdovico, L. Di Noto, I. Drachnev, D. Franco, C. Galbiati, C. Ghiano, M. Giammarchi, A. Goretti, Alexandre Göttel, M. Gromov, D. Güffanti, Aldo Ianni, Andrea Ianni, A. Jany, V. Kobychev, G. Korga, S. Kumaran, M. Laubenstein, E. Litvinovich, P. Lombardi, I. Lomskaya, L. Ludhová, G. Lukyanchenko, I. Machulin, J. Martýn, E. Meroni, L. Miramonti, M. Misiaszek, V. Muratova, R. Nugmanov, L. Oberauer, V. Orekhov, F. Ortica, M. Pallavicini, L. Papp, Luca Pelicci, Ö. Penek, L. Pietrofaccia, N. Pilipenko, A. Pocar, G. Raikov, M. T. Ranalli, G. Ranucci, A. Razeto, A. Re, M. Redchuk, N. Rossi, S. Schönert, D. Semenov, Giulio Settanta, O. Smirnov, A. Singhal, O. Smirnov, A. Sotnikov, R. Tartaglia, G. Testera, E. Unzhakov, F.L. Villante, A. Vishneva, R. B. Vogelaar, F. von Feilitzsch, M. Wójcik, M. Wurm, S. Zavatarelli, Κ. Zuber, G. Zuzel
Abstract
We present an improved measurement of the carbon-nitrogen-oxygen (CNO) solar neutrino interaction rate at Earth obtained with the complete Borexino Phase-III dataset. The measured rate, R_{CNO}=6.7_{-0.8}^{+2.0} counts/(day×100 tonnes), allows us to exclude the absence of the CNO signal with about 7σ C.L. The correspondent CNO neutrino flux is 6.6_{-0.9}^{+2.0}×10^{8} cm^{-2} s^{-1}, taking into account the neutrino flavor conversion. We use the new CNO measurement to evaluate the C and N abundances in the Sun with respect to the H abundance for the first time with solar neutrinos. Our result of N_{CN}=(5.78_{-1.00}^{+1.86})×10^{-4} displays a ∼2σ tension with the "low-metallicity" spectroscopic photospheric measurements. Furthermore, our result used together with the ^{7}Be and ^{8}B solar neutrino fluxes, also measured by Borexino, permits us to disfavor at 3.1σ C.L. the "low-metallicity" standard solar model B16-AGSS09met as an alternative to the "high-metallicity" standard solar model B16-GS98.