Neutrino mass limits from a precise determination of ββ-decay rates of 128Te and 130Te

Double beta decay of 128Te has been confirmed and the ratio of half-lives for ββ decay of 130Te and 128Te has been determiend as 130Te1/2/128Te1/2=(3.52±0.11)x10-4 by ion-counting mass spectrometry of Xe in ancient Te ores. The Xe measurements, combined with common Pb dating, yield a 130Te half-life of (2.7±0.1)x1021 yr and thus a 128Te half-life of (7.7±0.4)x1024 yr. These results give limits on the effective Majorana mass of the neutrino (<1.1-1.5 eV) and right-handed currents (|left-angle η right-angle |>5.3x10-8) 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 Z0 decay width