Neutrino mass limits from a precise determination of ββ-decay rates ofTe128andTe130

Double beta decay of ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ has been confirmed and the ratio of half-lives for ββ decay of ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ and ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ has been determiend as ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}_{1/2}^{}{}_{}{}^{}$ ${/}^{128}$ ${\mathrm{Te}}_{1/2}$=(3.52±0.11)×${10}^{\mathrm{-}4}$ by ion-counting mass spectrometry of Xe in ancient Te ores. The Xe measurements, combined with common Pb dating, yield a ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ half-life of (2.7±0.1)×${10}^{21}$ yr and thus a ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ half-life of (7.7±0.4)×${10}^{24}$ yr. These results give limits on the effective Majorana mass of the neutrino (<1.1-1.5 eV) and right-handed currents (‖〈η〉‖>5.3×${10}^{\mathrm{-}8)}$ comparable to the best obtained from direct neutrinoless ββ-decay searches. They also imply new limits on nonstandard Majorons not constrained by measurements of the ${\mathit{Z}}^0$ decay width.