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arXiv · 1601.05935

The Performance of the Muon Veto of the GERDA Experiment

K. Freund·R. Falkenstein·P. Grabmayr·A. Hegai·J. Jochum·M. Knapp·B. Lubsandorzhiev·F. Ritter·C. Schmitt·A. -K. Schütz·I. Jitnikov·E. Shevchik·M. Shirchenko·D. Zinatulina
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Abstract

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 $Q_{\beta\beta}$.

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K. Freund, R. Falkenstein, P. Grabmayr, A. Hegai, J. Jochum, M. Knapp, B. Lubsandorzhiev, F. Ritter, C. Schmitt, A. -K. Schütz, I. Jitnikov, E. Shevchik, M. Shirchenko, D. Zinatulina. 2016-01-22. The Performance of the Muon Veto of the GERDA Experiment. https://doi.org/10.1140/epjc/s10052-016-4140-7

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