First 0νββ results from EXO-200

We report on a search for neutrinoless double-beta decay of 136Xe with EXO-200. No signal is observed for a 136Xe exposure of 26.3 kg-yr, with a background of in the ±1σ region of interest. This sets a lower limit on the half-life of the neutrinoless double-beta decay , corresponding to effective Majorana masses of less than 140–380 meV, depending on the matrix element calculation.