Background model for the Majorana Demonstrator

The Majorana Collaboration is constructing a system containing 44 kg of high-purity Ge (HPGe) detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale to ∼15 meV. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 count/(ROI-t-y) in the 4 keV region of interest (ROI) around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials and analytical methods for background rejection, for example using powerful pulse shape analysis techniques profiting from the p-type point contact (PPC) HPGe detectors technology. The effectiveness of these methods is assessed using simulations of the different background components whose purity levels are constrained from radioassay measurements. Preliminary background results obtained during the engineering runs of the Demonstrator are presented.

[1]  J. C. Loach,et al.  The Majorana Demonstrator Radioassay Program , 2016, 1601.03779.

[2]  M. Weber,et al.  Search for Majorana neutrinos with the first two years of EXO-200 data , 2014, Nature.

[3]  M. Auger,et al.  Improved measurement of the 2νββ half-life of 136 Xe with the EXO-200 detector , 2014 .

[4]  J. Heise.  The Sanford Underground Research Facility at Homestake , 2014, 1503.01112.

[5]  D. Budjáš,et al.  Results on neutrinoless double-β decay of 76Ge from phase I of the GERDA experiment. , 2013, Physical review letters.

[6]  Rebecca Killick,et al.  An improved measurement of the 2\nu \beta \beta\ half-life of Xe-136 with EXO-200 , 2013, 1306.6106.

[7]  M. Decowski,et al.  Limit on neutrinoless ββ decay of 136Xe from the first phase of KamLAND-Zen and comparison with the positive claim in 76Ge. , 2012, Physical review letters.

[8]  J. C. Loach,et al.  The Majorana Demonstrator Neutrinoless Double-Beta Decay Experiment , 2012 .

[9]  Jing Liu,et al.  MaGe-a Geant4-Based Monte Carlo Application Framework for Low-Background Germanium Experiments , 2010, IEEE Transactions on Nuclear Science.

[10]  F. Šimkovic,et al.  0nubetabeta-decay nuclear matrix elements with self-consistent short-range correlations , 2009, 0902.0331.

[11]  J. Wilkerson,et al.  Neutrino Masses and Mixings: Status and Prospects , 2008 .

[12]  Frank T. Avignone,et al.  Double Beta Decay, Majorana Neutrinos, and Neutrino Mass , 2007, 0708.1033.

[13]  H. Klapdor-kleingrothaus,et al.  The evidence for the observation of 0ν beta beta decay: The identification of 0ν beta beta events from the full spectra. , 2006 .

[14]  E. al.,et al.  The IGEX experiment reexamined: a response to the critique of Klapdor-Kleingrothaus, Dietz, and Krivosheina , 2004, nucl-ex/0404036.

[15]  W. K. Hensley,et al.  The IGEX Ge-76 neutrinoless double beta decay experiment: Prospects for next generation experiments , 2002, hep-ex/0202026.

[16]  Limits on the Majorana neutrino mass in the 0.1-eV range , 1999, hep-ex/9902014.

[17]  M. Zrałek.  On the possibilities of distinguishing Dirac from Majorana neutrinos , 1997, hep-ph/9711506.

[18]  Steven R. Elliott,et al.  Double Beta Decay , 2011, 1110.6159.