Limits on Majoron-emitting double-βdecays of136Xe in the KamLAND-Zen experiment

A. Gando, Y. Gando, H. Hanakago, H. Ikeda, K. Inoue, R. Kato, M. Koga, S. Matsuda, T. Mitsui, T. Nakada, K. Nakamura, A. Obata (+27 others)
2012 Physical Review C  
We present limits on Majoron-emitting neutrinoless double-beta decay modes based on an exposure of 112.3 days with 125 kg of Xe-136. In particular, a lower limit on the ordinary (spectral index n = 1) Majoron-emitting decay half-life of Xe-136 is obtained as T_1/2^0νχ^0 > 2.6 x 10^24 yr at 90 corresponding upper limit on the effective Majoron-neutrino coupling, using a range of available nuclear matrix calculations, is < (0.8 - 1.6) x 10^-5. This excludes a previously unconstrained region of
more » ... ameter space and strongly limits the possible contribution of ordinary Majoron emission modes to 0νββ decay for neutrino masses in the inverted hierarchy scheme.
doi:10.1103/physrevc.86.021601 fatcat:gnddk726tvajtg26xkxty3fawe