Depth Requirements for a Tonne-scale 76Ge Neutrinoless Double-beta Decay Experiment
Abstract
Neutrinoless double-beta decay experiments can potentially determine the Majorana or Dirac nature of the neutrino, and aid in understanding the neutrino absolute mass scale and hierarchy. Future 76Ge-based searches target a half-life sensitivity of >10^27 y to explore the inverted neutrino mass hierarchy. Reaching this sensitivity will require a background rate of <1 count tonne^-1 y^-1 in a 4-keV-wide spectral region of interest surrounding the Q value of the decay. We investigate the overburden required to reach this background goal in a tonne-scale experiment with a compact (copper and lead) shield based on Monte Carlo calculations of cosmic-ray background rates. We find that, in light of the presently large uncertainties in these types of calculations, a site with an underground depth >~5200 mwe is required for a tonne-scale experiment with a compact shield similar to the planned 40-kg MAJORANA DEMONSTRATOR. The required overburden is highly dependent on the chosen shielding configuration and could be relaxed significantly if, for example, a liquid cryogen and water shield, or an active neutron shield were employed. Operation of the MAJORANA DEMONSTRATOR and GERDA detectors will serve to reduce the uncertainties on cosmic-ray background rates and will impact the choice of shielding style and location for a future tonne-scale experiment. 4/2013: The peer review process revealed that one of the veto rejection factors (the factor-of-4 described on p12) needs to be better established. Our reevaluation of this parameter to date has not yielded strong support for the value stated in the manuscript, and we require further study to develop a solid estimate. This further study will supersede the work described in this manuscript, and may or may not lead to the same conclusion regarding the ~>5200 mwe requirement for future tonne-scale 76Ge neutrinoless double beta decay experiments.
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Cite
@article{arxiv.1109.4154,
title = {Depth Requirements for a Tonne-scale 76Ge Neutrinoless Double-beta Decay Experiment},
author = {The MAJORANA Collaboration and E. Aguayo and F. T. Avignone and H. O. Back and A. S. Barabash and M. Bergevin and F. E. Bertrand and M. Boswell and V. Brudanin and M. Busch and Y-D. Chan and C. D. Christofferson and J. I. Collar and D. C. Combs and R. J. Cooper and J. A. Detwiler and P. J. Doe and Yu. Efremenko and V. Egorov and H. Ejiri and S. R. Elliott and J. Esterline and J. E. Fast and N. Fields and P. Finnerty and F. M. Fraenkle and V. M. Gehman and G. K. Giovanetti and M. P. Green and V. E. Guiseppe and K. Gusey and A. L. Hallin and R. Hazama and R. Henning and A. Hime and E. W. Hoppe and M. Horton and S. Howard and M. A. Howe and R. A. Johnson and K. J. Keeter and M. E. Keillor and C. Keller and J. D. Kephart and M. F. Kidd and A. Knecht and O. Kochetov and S. I. Konovalov and R. T. Kouzes and B. D. LaFerriere and B. H. LaRoque and J. Leon and L. E. Leviner and J. C. Loach and S. MacMullin and M. G. Marino and R. D. Martin and D. -M. Mei and J. H. Merriman and M. L. Miller and L. Mizouni and M. Nomachi and J. L. Orrell and N. R. Overman and D. G. Phillips and A. W. P. Poon and G. Perumpilly and G. Prior and D. C. Radford and K. Rielage and R. G. H. Robertson and M. C. Ronquest and A. G. Schubert and T. Shima and M. Shirchenko and K. J. Snavely and V. Sobolev and D. Steele and J. Strain and K. Thomas and V. Timkin and W. Tornow and I. Vanyushin and R. L. Varner and K. Vetter and K. Vorren and J. F. Wilkerson and B. A. Wolfe and E. Yakushev and A. R. Young and C. -H. Yu and V. Yumatov and C. Zhang},
journal= {arXiv preprint arXiv:1109.4154},
year = {2013}
}
Comments
Corresponding author: J. Detwiler ([email protected]), 25 pages, 2 figures