Precise determination of relative and absolute &#946;&#946;-decay rates of <SUP>128</SUP>Te and <SUP>130</SUP>Te

Double beta decay of 128Te has been confirmed and the ratio of half-lives for &#946;&#946; decay of 130Te and 128Te has been precisely determined as T&#189;130/T&#189;128=(3.52&#177;0.11)&#215;10-4 by ion-counting mass spectrometry of Xe in ancient Te ores, using techniques that reduce interferences due to trapped Xe. We have also detected excesses of 126Xe originating in high energy reactions of cosmic ray muons and their secondaries on Te; such reactions make minor contributions to the measured 128Xe excesses in the Te ores. The Xe measurements, combined with common Pb dating of the ores, yield a 130Te half-life of (2.7&#177;0.1)&#215;1021 yr and thus a 128Te half-life of (7.7&#177;0.4)&#215;1024 yr, the longest radioactive decay lifetime measured to date. These results give limits on the effective Majorana mass of the neutrino (&lt;1.1-1.5 eV) and right-handed currents (||&lt;&#951;&gt;||&lt;5.3&#215;10-8) comparable to the best obtained from direct neutrinoless &#946;&#946;-decay searches. They also imply new limits on unconventional Majorons not constrained by measurements of the Z0 decay width