First Evidence of pep Solar Neutrinos by Direct Detection in Borexino
G. Bellini et al. (Borexino Collaboration)
Phys. Rev. Lett. 108, 051302
Published 2 February 2012
doi:10.1103/PhysRevLett.108.051302  (preprint on arXiv)

Physics logothis paper have been been highlighted with a Synopsis on the Physics website: “Rare Fusion Reactions Probed with Solar Neutrinos”.


We observed, for the first time, solar neutrinos in the 1.0–1.5 MeV energy range.  We determined the rate of pep solar neutrino interactions in Borexino to be 3.1±0.6stat±0.3syst counts/(day x 100 ton).  Assuming the pep neutrino flux predicted by the standard solar model, we obtained a constraint on the CNO solar neutrino interaction rate of <7.9 counts/(day x 100 ton) (95% C.L.).  The absence of the solar neutrino signal is disfavored at 99.97% C.L., while the absence of the pep signal is disfavored at 98% C.L.  The necessary sensitivity was achieved by adopting data analysis techniques for the rejection of cosmogenic 11C, the dominant background in the 1–2 MeV region. Assuming the Mikheyev-Smirnov-Wolfenstein large mixing angle solution to solar neutrino oscillations, these values correspond to solar neutrino fluxes of (1.6±0.3) x 108 cm2 s-1 and <7.7 x 108 cm2 s-1 (95% C.L.) respectively, in agreement with both the high and low metallicity standard solar models.  These results represent the first direct evidence of the pep neutrino signal and the strongest constraint of the CNO solar neutrino flux to date.


First evidence of pep solar neutrinos by direct detection in Borexino

Leave a Reply