First Simultaneous Precision Spectroscopy of $pp$, $^7$Be, and $pep$ Solar Neutrinos with Borexino Phase-II

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Agostini, M. ; Altenmuller, K. ; Bravo, D. ; Wojcik, M. ; Wurm, M. ; Yokley, Z. ; Zaimidoroga, O. ; Zavatarelli, S. ; Zuber, K. ; Zuzel, G. ; Caccianiga, B. ; Calaprice, F. ; Caminata, A. ; Caprioli, S. ; Carlini, M. ; Cavalcante, P. ; Chepurnov, A. ; Choi, K. ; Collica, L. ; Appel, S. ; D'Angelo, D. ; Davini, S. ; Derbin, A. ; Ding, X. F. ; Di Ludovico, A. ; Di Noto, L. ; Drachnev, I. ; Fomenko, K. ; Formozov, A. ; Franco, D. ... view all 107 authors (2017)
  • Subject: Astrophysics - Solar and Stellar Astrophysics | High Energy Physics - Experiment

We present the first simultaneous measurement of the interaction rates of $pp$, $^7$Be, and $pep$ solar neutrinos performed with a global fit to the Borexino data in an extended energy range (0.19-2.93)$\,$MeV. This result was obtained by analyzing 1291.51$\,$days of Borexino Phase-II data, collected between December 2011 and May 2016 after an extensive scintillator purification campaign. We find: rate($pp$)$\,$=$\,$$134$$\,$$\pm$$\,$$10$$\,$($stat$)$\,$$^{\rm +6}_{\rm -10}$$\,$($sys$)$\,$cpd/100$\,$t, rate($^7$Be)$\,$=$\,$$48.3$$\,$$\pm$$\,$$1.1$$\,$($stat$)$\,$$^{\rm +0.4}_{\rm -0.7}$$\,$($sys$)$\,$cpd/100$\,$t, and rate($pep$)$\,$=$\,$$2.43$$\pm$$\,$$0.36$$\,$($stat$)$^{+0.15}_{-0.22}$$\,$($sys$)$\,$cpd/100$\,$t. These numbers are in agreement with and improve the precision of our previous measurements. In particular, the interaction rate of $^7$Be $\nu$'s is measured with an unprecedented precision of 2.7%, showing that discriminating between the high and low metallicity solar models is now largely dominated by theoretical uncertainties. The absence of $pep$ neutrinos is rejected for the first time at more than 5$\,$$\sigma$. An upper limit of $8.1$$\,$cpd/100$\,$t (95%$\,$C.L.) on the CNO neutrino rate is obtained by setting an additional constraint on the ratio between the $pp$ and $pep$ neutrino rates in the fit. This limit has the same significance as that obtained by the Borexino Phase-I (currently providing the tightest bound on this component), but is obtained by applying a less stringent constraint on the $pep$ $\nu$ flux.
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