1305.2405 (R. Agnese et al.)

Demonstration of Surface Electron Rejection with Interleaved Germanium
Detectors for Dark Matter Search    [PDF]

R. Agnese, A. J. Anderson, D. Balakishiyeva, R. Basu Thakur, D. A. Bauer, A. Borgland, D. Brandt, P. L. Brink, R. Bunker, B. Cabrera, D. O. Caldwell, D. G. Cerdeno, H. Chagani, M. Cherry, J. Cooley, B. Cornell, C. H. Crewdson, P. Cushman, M. Daal, P. C. F. Di Stefano, E. Do Couto E Silva, T. Doughty, L. Esteban, S. Fallows, E. Figueroa-Feliciano, J. Fox, M. Fritts, G. L. Godfrey, S. R. Golwala, J. Hall, H. R. Harris, J. Hasi, S. A. Hertel, B. A. Hines, T. Hofer, D. Holmgren, L. Hsu, M. E. Huber, A. Jastram, O. Kamaev, B. Kara, M. H. Kelsey, S. A. Kenany, A. Kennedy, C. J. Kenney, M. Kiveni, K. Koch, B. Loer, E. Lopez Asamar, R. Mahapatra, V. Mandic, C. Martinez, K. A. McCarthy, N. Mirabolfathi, R. A. Moffatt, D. C. Moore, P. Nadeau, R. H. Nelson, L. Novak, K. Page, R. Partridge, M. Pepin, A. Phipps, K. Prasad, M. Pyle, H. Qiu, R. Radpour, W. Rau, P. Redl, A. Reisetter, R. W. Resch, Y. Ricci, T. Saab, B. Sadoulet, J. Sander, R. Schmitt, K. Schneck, R. W. Schnee, S. Scorza, D. Seitz, B. Serfass, B. Shank, D. Speller, A. Tomada, A. N. Villano, B. Welliver, D. H. Wright, S. Yellin, J. J. Yen, B. A. Young, J. Zhang

SuperCDMS, a direct search for WIMPs, is currently operating a 9-kg array of cryogenic germanium (Ge) detectors in the Soudan Underground Laboratory. These detectors, known as iZIPs, use ionization and phonon sensors placed symmetrically on both sides of a Ge crystal to measure both charge and athermal phonons from each particle interaction. The information from each event provides excellent discrimination between electron recoils and nuclear recoils, as well as discrimination between events on the detector surface and those in the interior. To demonstrate the surface electron rejection capabilities, two $^{210}$Pb sources were installed facing detectors, producing $\sim$130 beta decays/hr. In $\sim$800 live hours, no events leaked into the WIMP signal region in the recoil energy range 8--115 keVr, providing an upper limit to the surface event leakage fraction of $1.7 \times 10^{-5}$ at 90% C.L. This rejection factor demonstrates that surface electrons would produce $< 0.6$ event background in the 0.3 ton-year exposure for the proposed 200-kg iZIP array in SuperCDMS SNOLAB.

View original: http://arxiv.org/abs/1305.2405