Neutrinoless ββ matrix element of 76 Ge from spectroscopic data

Effects of orbital occupancies on the neutrinoless ββ matrix element of 76 Ge

Majorons from Double Beta Decay *

We explain the existence of excess events near the endpoints of the double beta decay (ββ) spectra of several elements, using the neutrinoless emission of massless Goldstone bosons. Models with scalars carrying lepton number −2 are proposed for this purpose so that ordinary neutrinoless ββ is forbidden, and we can raise the scale of global symmetry breaking above the 10 keV scale needed for obs...

Exact evaluation of the nuclear form factor for new kinds of majoron emission in neutrinoless double beta decay ∗

We have developed a formalism, based on the Fourier-Bessel expansion, that facilitates the evaluation of matrix elements involving nucleon recoil operators, such as appear in serveral exotic forms of neutrinoless double beta decay (ββ 0ν). The method is illustrated by applying it to the " charged " majoron model, which is one of the few that can hope to produce an observable effect. From our nu...

Analysis around Q ββ for 76 Ge Double Beta Decay experiments , and Statistics at Low Count Rates

The background in the region of the Q-value for neutrinoless double beta decay of Ge has been investigated by different methods: Simulation with GEANT 4 of the HEIDELBERG-MOSCOW experiment, analysis of other Ge double beta experiments. Statistical features of the analysis at very low count rates are discussed.

Limit on neutrinoless ββ decay of 136Xe from the first phase of KamLAND-Zen and comparison with the positive claim in 76Ge.

We present results from the first phase of the KamLAND-Zen double-beta decay experiment, corresponding to an exposure of 89.5 kg yr of (136)Xe. We obtain a lower limit for the neutrinoless double-beta decay half-life of T(1/2)(0ν)>1.9×10(25) yr at 90% C.L. The combined results from KamLAND-Zen and EXO-200 give T(1/2)(0ν)>3.4×10(25) yr at 90% C.L., which corresponds to a Majorana neutrino mass l...