Münster 2017 – scientific programme

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T: Fachverband Teilchenphysik

T 107: Neutrinophysik 8

T 107.8: Talk

Thursday, March 30, 2017, 18:30–18:45, H 2

Update on the 8B analysis with the Borexino detector — •Simon Appel for the Borexino collaboration — simon.appel@ph.tum.de

Borexino is a liquid scintillator based real-time neutrino detector with a target mass of 278t, located at the Laboratori Nationali del Gran Sasso. Due to its low energy threshold of 100*keV, Borexino was able to perform the first real-time measurement of 7Be and pp neutrinos. Furthermore it is also sensitive to 8B neutrinos, which is main topic of this talk. The 8B analysis is limited to a lower energy threshold of 3*MeV by external gamma background. As the expected event rate is in the order of only 0.2-0.3 counts per day, it is crucial to have a profound knowledge of the different background sources. Especially radio-isotopes produced by muons are a major source of background for this analysis. To veto these events one has to identify cosmic muons crossing Borexino, which is realized with a water cherenkov veto in the outer detector and a pulse shape analysis in the inner detector. A time cut after each muon reduces background induced by comsogenically produced radio-isotopes. In the presented analysis it was possible to suppress all the backgrounds to a negligible value. This allows to detect solar 8B neutrinos in Borexino and thus makes it possible to confirm the MSW-LMA solution. This talk will give an update on this analysis within the Borexino detector framework. This work is funded by the DFG and the Exzellenzcluster Universe Munich.