196 Pages

Cosmic background discrimination for the rare neutrino event search in BOREXINO and LENA [Elektronische Ressource] / Michael Wurm

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AbstractThe level of cosmogenic background is of great importance for the search for very rareneutrino events in a liquid-scintillator detector: Exact knowledge of the cosmic muon,cosmogenic neutron and radioisotope background is e ential for solar neutrino detec-tion inBorexino; it also has considerable impact on the design of the next-generationLENA experiment.In the present work, the performance of the muon identi cation tags applied inBorexino was evaluated to precisely determine the residual muon rate contaminatingthe neutrino data sample. While the veto e ciency for cosmic muons is more than suf- cient for solar neutrino analysis, the muon-induced in-situ production of radionuclidesinside the detection volume presents a challenging background. Especially regarding11the search for CNO and pep neutrinos, the rate of cosmogenic C decays exceedsthe expected neutrino signal by at least one order of magnitude. A measurement byBorexino of these up to now undetermined branches of solar neutrino production will11only succeed if the subtraction of the C events becomes po ible on an event-by-eventbasis. The muon track reconstruction devised in this thesis is mandatory for this task:The spacial information on the track is on the one hand basis for the threefold coinci-11dence veto used in the direct tagging of C decay events.



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Published 01 January 2009
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Language English
Document size 9 MB