DAMA/LXe results on Charge-Non-Conserving processes

The electric charge conservation is a fundamental law of quantum electrodynamics; nevertheless, because there is the possibility that it may be broken in future unified gauge theories, many efforts have been devoted to test it with different procedures by various experimental groups.

In particular, by using the ~6.5 kg LXe set-up, upgraded several times during the years to improve its performances, we have achieved the results summarized in the following:

1996 - With the detector filled with Kr-free Xenon enriched in 129Xe at 99.95%, the following limits on electron stability (considering K-shell electrons) were obtained for the processes

    e- → 3ν, majoron + ν or anything invisible (exposure of 634 kg day):
    τ > 1.5 x 1023 y at 68% C.L.
    e- -> ν e + γ (exposure of 70 kg day):
    τ > 2.0 x 1025 y at 68% C.L.
1999 - New lifetime limits on the charge non-conserving electron capture with excitation of 129Xe nuclear levels have been established by using an exposure of 823.1 kg day. These limits are in the range: (1-4) x 1024 y at 90% C.L., for the different excited levels of 129Xe. The derived restrictions on the relative strengths of the charge non-conserving (CNC) processes are (90% C.L.):
W)2 < 2.2 x 10-26 and (εγ)2 < 1.3 x 10-42