Abstract
We present an improved search for neutrinoless double-beta (0νββ) decay of Xe136 in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a significant reduction of the Ag110m contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the 0νββ decay half-life of T1/20ν>1.07×1026 yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasidegenerate neutrino mass region.
Original language | English (US) |
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Article number | 082503 |
Journal | Physical Review Letters |
Volume | 117 |
Issue number | 8 |
DOIs | |
State | Published - Aug 16 2016 |
ASJC Scopus subject areas
- General Physics and Astronomy