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
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 νe-equivalent 7Be solar neutrino flux of 3.10[±0.15]×109 cm−2 s−1 and, under the assumption of νe 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.