Precision measurement of the 7Be solar neutrino interaction rate in Borexino

Precision Measurement of the ⁷Be Solar Neutrino Interaction Rate in Borexino
G. Bellini et al. (Borexino Collaboration)
Phys. Rev. Lett. 107, 141302
Published 30 September 2011

doi:10.1103/PhysRevLett.107.141302  (preprint on arXiv)

Abstract

The rate of neutrino-electron elastic scattering interactions from 862 keV ⁷Be solar neutrinos in Borexino is determined to be 46.0[±1.5](stat) [+1.5 −1.6](syst) counts/(day⋅100 ton).  This corresponds to a ν_e-equivalent ⁷Be solar neutrino flux of 3.10[±0.15]×10⁹ cm⁻² s⁻¹ and, under the assumption of ν_e transition to other active neutrino flavours, yields an electron neutrino survival probability of 0.51[±0.07] at 862 keV.  The no flavor change hypothesis is ruled out at 5.0 σ.  A global solar neutrino analysis with free fluxes determines Φpp=6.06[+0.02 −0.06]×10¹⁰ cm⁻² s⁻¹ and  ΦCNO<1.3×10⁹ cm⁻² s⁻¹ (95% C.L.).  These results significantly improve the precision with which the Mikheyev-Smirnov-Wolfenstein large mixing angle neutrino oscillation model is experimentally tested at low energy.