130Te and 128Te double beta decay half-lives

The double beta decay half-lives of 130Te measured in geological Te specimens of known age fall into two distinct groups: 2.5±0.4×1021 yr and 8±1×1020 yr. Discussion about which value is correct has lasted for more than 30 years without a satisfactory resolution. Since the ratio of the 130Te half-life to that of 128Te is known (3.74±0.11×10−4), the 128Xe half-life, which constrains the effective Majorana mass of the neutrino, also becomes uncertain within this factor of ∼3. Here we describe several experiments and observations, which lead us to the conclusion that the “short” half-lives are more likely to be correct. This is in agreement with preliminary results recently obtained in the direct counting NEMO-3 experiment.