New limit on neutrinoless double β decay in ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ with a time projection chamber

A xenon time projection chamber with an active volume of 207 L has been built to study neutrinoless double β decay in ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$. Data were taken in the Gotthard Underground Laboratory, with 5 atm of xenon enriched to 62.5% in ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$. From 3380 h of data, no evidence has been found for the 0ν $0^{+}$→$0^{+}$ transition. Half-life limits of ${\mathit{T}}_{1/2}^{0\nu }$>2.5(4.9)×${10}^{23}$ yr in the mass-mechanism mode and ${\mathit{T}}_{1/2}^{0\nu }$>1.7(3.2)×${10}^{23}$ 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.