2012: Absence of day-night asymmetry of 862 keV Be-7 solar neutrino rate in Borexino and MSW oscillation

Physics Letters B
Volume 707, Issue 1, 16 January 2012, Pages 22–26

G. Bellini et al. (Borexino Collaboration) M. Wójcik, G. Zuzel, M. Misiaszek

Download: http://www.sciencedirect.com/science/article/pii/S037026931101389X


We report the result of a search for a day–night asymmetry in the 7Be solar neutrino interaction rate in the Borexino detector at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. The measured asymmetry is Adn=0.001±0.012 (stat)±0.007 (syst), in agreement with the prediction of MSW-LMA solution for neutrino oscillations. This result disfavors MSW oscillations with mixing parameters in the LOW region at more than 8.5 σ. This region is, for the first time, strongly disfavored without the use of reactor anti-neutrino data and therefore the assumption of CPT symmetry. The result can also be used to constrain some neutrino oscillation scenarios involving new physics.