The Performance of the Muon Veto of the GERDA Experiment

• Published in: arXiv.org 2016-01
• Main Authors: Freund, K, Falkenstein, R, Grabmayr, P, Hegai, A, Jochum, J, Knapp, M, Lubsandorzhiev, B, Ritter, F, Schmitt, C, A -K Schütz, Jitnikov, I, Shevchik, E, Shirchenko, M, Zinatulina, D
• Format: Article
• Language: English
• Subjects: Beta decay; Computer simulation; Germanium; Monte Carlo simulation; Muons
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1601.05935

Low background experiments need a suppression of cosmogenically induced events. The GERDA experiment located at LNGS is searching for the neutrinless double beta decay of \(^{76}\)Ge. It is equipped with an active muon veto the main part of which is a water Cherenkov veto with 66 PMTs in the watertank surrounding the GERDA cryostat. With this system 806 live days have been recorded, 491 days were combined muon-germanium data. A muon detection efficiency of \(\varepsilon_{\mu d}=(99.935\pm0.015)\) \% was found in a Monte Carlo simulation for the muons depositing energy in the germanium detectors. By examining coincident muon-germanium events a rejection efficiency of \(\varepsilon_{\mu r}=(99.2_{-0.4}^{+0.3})\) \% was found. Without veto condition the muons by themselves would cause a background index of \(\textrm{BI}_{\mu}=(3.16 \pm 0.85)\times10^{-3}\) cts/(keV\(\cdot\)kg\(\cdot\)yr) at \(Q_{\beta\beta}\).