The Milano experiment on double beta decay of 136Xe

Abstract

An experiment on double beta decay of 136Xe has been performed at the Gran Sasso Underground Laboratory. The detector was a multicell proportional counter, built from selected low background materials, which was filled alternatively with natural xenon, enriched xenon to 64% in the 136Xe isotope, and natural xenon cleaned by ultracentrifugation, and heavily shielded against environmental radioactivity. After 6000 hours of operation the half-lifetime for the neutrinoless decay mode turns out to be greater than 2*1022 y at 90% CL. A limit of 6*1019 y, also at 90% CL, is reported for the 2 nu decay mode.