High precision ⁷Be solar neutrinos measurement and day night effect obtained with Borexino

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• 作者：G. Testera ; G. Bellini ; J. Benziger ; D. Bick ; S. Bonetti ; G. Bonfini ; B. Caccianiga ; L. Cadonati ; F. Calaprice ; C. Carraro ; A. Chavarria ; D. D'Angelo ; A. Derbin ; A. Etenko ; K. Fomenko ; D. Franco ; C. Galbiati ; S. Gazzana ; C. Ghiano ; M. Giammarchi ; et al.
• 关键词：Solar neutrinos ; Neutrino oscillations ; Low background detectors ; Liquid scintillators
• 刊名：Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
• 出版年：2012
• 出版时间：11 November, 2012
• 年：2012
• 卷：692
• 期：Complete
• 页码：258-261
• 全文大小：305 K

文摘

We report the direct measurement of the ⁷Be solar neutrino signal rate performed with the Borexino detector at the Laboratori Nazionali del Gran Sasso and the search for a day-night asymmetry of this interaction rate. The interaction rate of the 0.862 MeV ⁷Be neutrinos is counts/(day 100 ton). The hypothesis of no oscillation for this solar neutrinos is inconsistent with our measurement at the C.L. Our result is the first direct measurement of solar neutrinos with an accuracy better than 5 % . We report the survival probability for solar in the transition region between matter-enhanced and vacuum-driven oscillations. The measured day night asymmetry is (stat)¡À0.007 (syst), in agreement with the predicition of MSW-LMA neutrino oscillations. This result discourages MSW oscillations with mixing parameters in the LOW region at more than , meaning that this region is, for the first time, strongly rejected without the assumption of CPT symmetry. The result can also be used to constrain some neutrino oscillation scenarios involving new physics.