Bonn 2010 – scientific programme

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T: Fachverband Teilchenphysik

T 108: Niederenergie-Neutrinophysik und Suche nach dunkler Materie II

T 108.2: Talk

Tuesday, March 16, 2010, 17:00–17:15, HG XI

Background suppression strategies in Borexino for solar pep and CNO neutrino spectroscopy — •Werner Maneschg — Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg

Borexino is a real-time experiment for low-energy neutrino spectroscopy, operating since May 2007 at the underground Gran Sasso National Laboratories. The high radiopurity achieved and statistics collected up to now (approx. 600 days of live time) allows to study week signals from different types of neutrinos. The present talk is focused on the study of the solar neutrino fluxes from the pep fusion process and the CNO cycle. The main background considered here is 11C induced by the in-situ muon flux. In 95% of cases a neutron is released by the parent 12C. The threefold coincidence consisting of (1) the parent muon, (2) the 2.2 MeV gamma-ray from neutron capture on proton and (3) the decay of 11C allows to tag 11C on event-by-event basis and to determine physical properties of the involved particles. Another relevant background component is given by the gamma rays from 208Tl decays in materials in the outer parts of the detector. A calibration with an external 228Th source and Monte-Carlo simulations are used for its characterization. The strategy for the global spectral fit analysis of pep and CNO neutrinos is finally presented.