@article{bdd9ca484f694db38cc41c4dfb738f5e,
title = "Search for Majorana neutrinos with the first two years of EXO-200 data",
abstract = "Many extensions of the standardmodel of particle physics suggest that neutrinos should be Majorana-type fermions-that is, that neutrinos are their own anti-particles-but this assumption is difficult to confirm. Observation of neutrinoless double-b decay (0nbb), a spontaneous transition that may occur in several candidate nuclei, would verify the Majorana nature of the neutrino and constrain the absolute scale of the neutrino mass spectrum. Recent searches carried out with 76Ge (the GERDA experiment) and 136Xe (the KamLAND-Zen and EXO (Enriched Xenon Observatory)-200 experiments) have established the lifetime of this decay to be longer than 1025 years, corresponding to a limit on the neutrino mass of 0.2-0.4 electronvolts. Herewereport newresults fromEXO-200 basedon a large 136Xeexposure that representsan almost fourfold increase from our earlier published data sets. We have improved the detector resolution and revised the data analysis. The half-life sensitivity we obtain is 1.9x1025 years, an improvement by a factor of 2.7 on previous EXO-200 results. We find no statistically significant evidence for 0nbb decay and set a half-life limit of 1.1x10 25 years at the 90 per cent confidence level. The high sensitivity holds promise for further running of the EXO-200 detector and future 0nbb decay searches with an improved Xe-based experiment, nEXO.",
author = "{The EXO-200 Collaboration} and Albert, {J. B.} and Auty, {D. J.} and Barbeau, {P. S.} and E. Beauchamp and D. Beck and V. Belov and C. Benitez-Medina and J. Bonatt and M. Breidenbach and T. Brunner and A. Burenkov and Cao, {G. F.} and C. Chambers and J. Chaves and B. Cleveland and M. Coon and A. Craycraft and T. Daniels and M. Danilov and Daugherty, {S. J.} and Davis, {C. G.} and J. Davis and R. DeVoe and S. Delaquis and T. Didberidze and A. Dolgolenko and Dolinski, {M. J.} and M. Dunford and W. Fairbank and J. Farine and W. Feldmeier and P. Fierlinger and D. Fudenberg and G. Giroux and R. Gornea and K. Graham and G. Gratta and C. Hall and S. Herrin and M. Hughes and Jewell, {M. J.} and Jiang, {X. S.} and A. Johnson and Johnson, {T. N.} and S. Johnston and A. Karelin and Kaufman, {L. J.} and R. Killick and T. Koffas and S. Kravitz",
note = "Funding Information: Acknowledgements EXO-200 is supported by the DOE and NSF in the United States, NSERC in Canada, SNF in Switzerland, NRF in Korea, RFBR (12-02-12145) in Russia and the DFG Cluster of Excellence {\textquoteleft}Universe{\textquoteright} in Germany. EXO-200 data analysis and simulation used resources of the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the US DOE under contract no. DE-AC02-05CH11231. The EXO-200 collaboration acknowledges the WIPP for their hospitality.",
year = "2014",
month = jun,
day = "1",
doi = "10.1038/nature13432",
language = "English (US)",
volume = "510",
pages = "229--234",
journal = "Nature",
issn = "0028-0836",
publisher = "Nature Publishing Group",
number = "7504",
}