Search for Neutrinoless Double-Beta Decay in ${}^{136}$Xe with EXO-200

Abstract

We report on a search for neutrinoless double-beta decay of ${}^{136}$Xe with EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background of ~1.5 x 10^{-3} /(kg yr keV) in the $\pm 1\ddot{I}ƒ$ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay $T_{1/2}^{0\hat{I}½{\hat{I}}^2{\hat{I}}^2}$(${}^{136}$Xe) > 1.6 x 10${}^{25}$ yr (90% CL), corresponding to effective Majorana masses of less than 140-380 meV, depending on the matrix element calculation.