New Limit On Neutrinoless Double Beta-Decay In Xe-136 With A Time Projection Chamber

A xenon time projection chamber with an active volume of 207 L has been built to study neutrinoless double beta-decay in Xe-136. Data were taken in the Gotthard Underground Laboratory, with 5 atm of xenon enriched to 62.5% in Xe-136. From 3380 h of data, no evidence has been found for the 0v 0+ --> 0+ transition. Half-life limits of T1/2(0v) > 2.5(4.9) x 10(23) yr in the mass-mechanism mode and T1/2(0v) > 1.7 (3.2) x 10(23) yr in the right-handed-current mode, at the 90(68)% C.L., were derived. An upper limit for the Majorana neutrino mass parameter was deduced.