Source-linked AI summary
Search for Majorana Neutrinos with the Complete KamLAND-Zen Dataset
S. Abe, T. Araki, K. Chiba, T. Eda, M. Eizuka, Y. Funahashi, A. Furuto, A. Gando, Y. Gando, S. Goto, T. Hachiya, K. Hata, K. Ichimura, S. Ieki, H. Ikeda, K. Inoue, K. Ishidoshiro, Y. Kamei, N. Kawada, Y. Kishimoto, M. Koga, A. Marthe, Y. Matsumoto, T. Mitsui, H. Miyake, D. Morita, R. Nakajima, K. Nakamura, R. Nakamura, R. Nakamura, J. Nakane, T. Ono, H. Ozaki, K. Saito, T. Sakai, I. Shimizu, J. Shirai, K. Shiraishi, A. Suzuki, K. Tachibana, K. Tamae, H. Watanabe, K. Watanabe, S. Yoshida, S. Umehara, K. Fushimi, K. Kotera, Y. Urano, B. E. Berger, B. K. Fujikawa, J. G. Learned, J. Maricic, Z. Fu, S. Ghosh, J. Smolsky, L. A. Winslow, Y. Efremenko, H. J. Karwowski, D. M. Markoff, W. Tornow, S. Dell'Oro, T. O'Donnell, J. A. Detwiler, S. Enomoto, M. P. Decowski, K. M. Weerman, C. Grant, O. Penek, H. Song, A. Li, S. N. Axani, M. Garcia, M. Sarfraz
TL;DR
An improved search covering the unexplored inverted-ordering region is needed to test theoretical models predicting ⟨mββ⟩ there. A simultaneous likelihood fit uses binned singles-data and long-lived-data energy spectra, with systematic uncertainties profiled. The 0νββ half-life lower limit is 3.5 × 10^26 yr (90% C.L.).
Problem
An improved search covering the unexplored inverted-ordering region is needed to test theoretical models predicting ⟨mββ⟩ there [4–6].
Source: p. 2Method
A simultaneous likelihood fit uses binned singles-data and long-lived-data energy spectra, with systematic uncertainties profiled.
Source: p. 4Results
The 0νββ half-life lower limit is 3.5 × 10^26 yr (90% C.L.).
Source: p. 4Takeaways & Limitations
KamLAND-Zen provides the most stringent tests of ⟨mββ⟩ in the inverted-ordering region and several theoretical models.
Source: p. 5The quoted mass limits use phenomenological NME calculations that omit quenching physics and short-range contact contributions included in newer calculations.
Source: p. 5
Abstract
from arXiv · showhide
We present a search for neutrinoless double-beta ($0\nu\beta\beta$) decay of $^{136}$Xe using the full \mbox{KamLAND-Zen 800} dataset with 745\,kg of enriched xenon, corresponding to an exposure of $2.1$\,ton\,yr of $^{136}$Xe. This updated search benefits from a more than twofold increase in exposure, recovery of photo-sensor gain, and reduced background from muon-induced spallation of xenon. Combining with the search in the previous KamLAND-Zen phase, we obtain a lower limit for the $0\nu\beta\beta$ decay half-life of $T_{1/2}^{0\nu} > 3.8 \times 10^{26}$\,yr at 90\% C.L., a factor of 1.7 improvement over the previous limit. The corresponding upper limits on the effective Majorana neutrino mass are in the range 28--122\,meV using phenomenological nuclear matrix element calculations.