Limits on Majoron-emitting double-beta decays of Xe-136 in the KamLAND-Zen experiment

作者：Gando A^*; Gando Y; Hanakago H; Ikeda H; Inoue K; Kato R; Koga M; Matsuda S; Mitsui T; Nakada T; Nakamura K; Obata A; Oki A; Ono Y; Shimizu I; Shirai J; Suzuki A; Takemoto Y; Tamae K; Ueshima K; Watanabe H; Xu B D; Yamada S; Yoshida H; Kozlov A; Yoshida S; Banks T I; Detwiler J A; Freedman S J; Fujikawa B K; Han K; O' Donnell T; Berger B E; Efremenko Y; Karwowski H J; Markoff D M; Tornow W; Enomoto S

来源：Physical Review C, 2012, 86(2): 021601.

DOI：10.1103/PhysRevC.86.021601

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 136Xe is obtained as T-1/2(0 nu chi 0) %26gt; 2.6 x 10(24) 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 %26lt; g(ee)%26gt; %26lt; (0.8-1.6) x 10(-5). This excludes a previously unconstrained region of parameter space and strongly limits the possible contribution of ordinary Majoron emission modes to 0 nu beta beta decay for neutrino masses in the inverted hierarchy scheme.

• 出版日期2012-8-6