An improved measurement of the 2νββ half-life of Xe-136 with EXO-200

J. B. Albert, M. Auger, D. J. Auty, P. S. Barbeau, E. Beauchamp, D. Beck, V. Belov, C. Benitez-Medina, J. Bonatt, M. Breidenbach, T. Brunner, A. Burenkov, G. F. Cao, C. Chambers, J. Chaves, B. Cleveland, S. Cook, T. Daniels, M. Danilov, S. J. Daugherty, C. G. Davis, J. Davis, S. Delaquis, R. DeVoe, A. Dobi, M. J. Dolinski, A. Dolgolenko, M. Dunford, W. Fairbank Jr., J. Farine, W. Feldmeier, P. Fierlinger, D. Franco, D. Fudenberg, G. Giroux, R. Gornea, K. Graham, G. Gratta, C. Hall, K. Hall, C. Hargrove, S. Herrin, M. Hughes, X. S. Jiang, A. Johnson, T. N. Johnson, S. Johnston, A. Karelin, L. J. Kaufman, R. Killick, S. Kravitz, A. Kuchenkov, K. S. Kumar, D. S. Leonard, F. Leonard, C. Licciardi, R. MacLellan, M. G. Marino, B. Mong, M. Montero Díez, D. Moore, R. Nelson, A. Odian, I. Ostrovskiy, K. O'Sullivan, C. Ouellet, A. Piepke, A. Pocar, C. Y. Prescott, A. Rivas, P. C. Rowson, M. P. Rozo, J. J. Russell, A. Sabourov, D. Sinclair, K. Skarpaas, S. Slutsky, V. Stekhanov, V. Strickland, M. Tarka, T. Tolba, D. Tosi, K. Twelker, P. Vogel, J. -L. Vuilleumier, A. Waite, J. Walton, T. Walton, M. Weber, L. J. Wen, U. Wichoski, J. Wodin, J. D. Wright, L. Yang, Y. -R. Yen, O. Ya. Zeldovich, Y. B. Zhao

Published 2013-06-25, updated 2014-01-29Version 4

We report on an improved measurement of the 2\nu \beta \beta\ half-life of Xe-136 performed by EXO-200. The use of a large and homogeneous time projection chamber allows for the precise estimate of the fiducial mass used for the measurement, resulting in a small systematic uncertainty. We also discuss in detail the data analysis methods used for double-beta decay searches with EXO-200, while emphasizing those directly related to the present measurement. The Xe-136 2\nu \beta \beta\ half-life is found to be 2.165 +- 0.016 (stat) +- 0.059 (sys) x 10^21 years. This is the most precisely measured half-life of any 2\nu \beta \beta\ decay to date.