The background in the neutrinoless double beta decay experiment GERDA
Abstract
The GERmanium Detector Array (GERDA) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta decay of 76Ge. The signature of the signal is a monoenergetic peak at 2039 keV, the Q-value of the decay, Q_bb. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around Q_bb. The main parameters needed for the neutrinoless double beta decay analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around Q_bb with a background index ranging from 17.6 to 23.8*10^{-3} counts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at Q-bb is dominated by close sources, mainly due to 42K, 214Bi, 228Th, 60Co and alpha emitting isotopes from the 226Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known gamma peaks, the energy spectrum can be fitted in an energy range of 200 kev around Q_bb with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.
Keywords
Cite
@article{arxiv.1306.5084,
title = {The background in the neutrinoless double beta decay experiment GERDA},
author = {The GERDA collaboration and M. Agostini and M. Allardt and E. Andreotti and A. M. Bakalyarov and M. Balata and I. Barabanov and M. Barnabe Heider and N. Barros and L. Baudis and C. Bauer and N. Becerici-Schmidt and E. Bellotti and S. Belogurov and S. T. Belyaev and G. Benato and A. Bettini and L. Bezrukov and T. Bode and V. Brudanin and R. Brugnera and D. Budjas and A. Caldwell and C. Cattadori and A. Chernogorov and F. Cossavella and E. V. Demidova and A. Domula and V. Egorov and R. Falkenstein and A. Ferella and K. Freund and N. Frodyma and A. Gangapshev and A. Garfagnini and C. Gotti and P. Grabmayr and V. Gurentsov and K. Gusev and K. K. Guthikonda and W. Hampel and A. Hegai and M. Heisel and S. Hemmer and G. Heusser and W. Hofmann and M. Hult and L. V. Inzhechik and L. Ioannucci and J. Janicsko Csathy and J. Jochum and M. Junker and T. Kihm and I. V. Kirpichnikov and A. Kirsch and A. Klimenko and K. T. Knoepfle and O. Kochetov and V. N. Kornoukhov and V. V. Kuzminov and M. Laubenstein and A. Lazzaro and V. I. Lebedev and B. Lehnert and H. Y. Liao and M. Lindner and I. Lippi and X. Liu and A. Lubashevskiy and B. Lubsandorzhiev and G. Lutter and C. Macolino and A. A. Machado and B. Majorovits and W. Maneschg and I. Nemchenok and S. Nisi and C. O'Shaughnessy and D. Palioselitis and L. Pandola and K. Pelczar and G. Pessina and A. Pullia and S. Riboldi and C. Sada and M. Salathe and C. Schmitt and J. Schreiner and O. Schulz and B. Schwingenheuer and S. Schoenert and E. Shevchik and M. Shirchenko and H. Simgen and A. Smolnikov and L. Stanco and H. Strecker and M. Tarka and C. A. Ur and A. A. Vasenko and O. Volynets and K. von Sturm and V. Wagner and M. Walter and A. Wegmann and T. Wester and M. Wojcik and E. Yanovich and P. Zavarise and I. Zhitnikov and S. V. Zhukov and D. Zinatulina and K. Zuber and G. Zuzel},
journal= {arXiv preprint arXiv:1306.5084},
year = {2014}
}