Hamburg 2016 – scientific programme

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T: Fachverband Teilchenphysik

T 78: Niederenergie-Neutrinophysik II

T 78.9: Talk

Wednesday, March 2, 2016, 18:45–19:00, VMP9 SR 07

Reducing deadtime with a modified Li-He veto in BoreXino — •Stefan Weinz and Michael Wurm — Physics Institute, University of Mainz

Although the BoreXino detector is located in a deep underground lab in Gran Sasso with huge of rock overburden (≈ 3500m water equivalent), a non-negligible flux of high energetic cosmic muons is still able to penetrate the fiducial volume of the detector. These muons can be tagged with high efficiency, but more dangerously, a muon passing the detector may interact with the ¹²C nuclei of the liquid scintillator, thus creating cosomogenic radioisotopes. A prominent example for these unstable nuclei are ⁸He and ⁹Li isotopes, whose decay products can mimic very well the ν-signature of inverse β-decay. To suppress this serious background source, the common strategy in BoreXino is to simply veto the whole fiducial volume for two seconds, introducing an overall deadtime of ≈ 10%. This muon-induced deadtime can be greatly reduced by introducing cuts based on the study of muon properties which may be related to the production of ⁸He and ⁹Li isotopes. The talk presents the muons cuts in three observables as well as their performance and limitations.