Limits on Majoron-emitting double-β decays of 136Xe in the KamLAND-Zen experiment
Abstract
We present limits on Majoron-emitting neutrinoless double-β decay modes based on an exposure of 112.3 days with 125 kg of 136Xe. In particular, a lower limit on the ordinary (spectral index n=1) Majoron-emitting decay half-life of 136Xe is obtained as T1/20νχ0>2.6×1024 yr at 90% C.L., a factor of five more stringent than previous limits. The corresponding upper limit on the effective Majoron-neutrino coupling, using a range of available nuclear matrix calculations, is <gee><(0.8-1.6)×10-5. This excludes a previously unconstrained region of parameter space and strongly limits the possible contribution of ordinary Majoron emission modes to 0νββ decay for neutrino masses in the inverted hierarchy scheme.
- Publication:
-
Physical Review C
- Pub Date:
- August 2012
- DOI:
- 10.1103/PhysRevC.86.021601
- arXiv:
- arXiv:1205.6372
- Bibcode:
- 2012PhRvC..86b1601G
- Keywords:
-
- 23.40.-s;
- 21.10.Tg;
- 14.60.Pq;
- 27.60.+j;
- Beta decay;
- double beta decay;
- electron and muon capture;
- Lifetimes;
- Neutrino mass and mixing;
- 90<
- =A<
- =149;
- High Energy Physics - Experiment;
- Nuclear Experiment
- E-Print:
- 4 pages, 3 figures (1 figure added). Published version in PRC rapid communication