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Author Bongrand, Mathieu
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword NUCLEAR PHYSICS AND RADIATION PHYSICS ♦ PHYSICS OF ELEMENTARY PARTICLES AND FIELDS ♦ BETA SOURCES ♦ DOUBLE BETA DECAY ♦ ELECTRONS ♦ ENERGY RESOLUTION ♦ EV RANGE ♦ GAMMA SPECTROSCOPY ♦ HIGH-PURITY GE DETECTORS ♦ LEPTON NUMBER ♦ MOLYBDENUM 100 ♦ NATURAL RADIOACTIVITY ♦ NEUTRINOS ♦ NUCLEAR MATRIX ♦ RADON ♦ REST MASS ♦ SELENIUM 82 ♦ SENSITIVITY ♦ SHOWER COUNTERS ♦ UNDERGROUND ♦ YIELDS
Abstract The NEMO-3 experiment was devoted to the research of the neutrinoless double beta decay and the precise measurement of the two-neutrino double beta decay of seven isotopes. The detector took data in the Laboratoire Souterrain de Modane (LSM) from 2003 to 2011. The unique combination of a 3D-tracker and a calorimeter allowed to fully reconstruct the double beta decay events topology and strongly reduces the backgrounds. This feature also permitted to characterize the remaining backgrounds in independent analysis channels. With an exposure of 34.7 kg·y of {sup 100}Mo no evidence for the 0ν2β signal has been found, yielding a limit for the light Majorana neutrino mass mechanism of T{sub 1/2}(0ν2β) > 1.1 10{sup 24} years (90 % C.L.) once both statistical and systematic uncertainties are taken into account. Depending on the Nuclear Matrix Elements this corresponds to an upper limit on the Majorana effective neutrino mass of |m{sub ββ}| < 0.3 − 0.9 eV (90 % C.L.). Constraints on other lepton number violating mechanisms of 0ν2β decays are also given. Searching for high-energy double electron events in all suitable sources of the detector, no event in the energy region [3.2-10] MeV is observed for an exposure of 47 kg·y. The next generation experiment, SuperNEMO, will use the same experimental technique to extend the sensitivity on the neutrinoless double beta decay search. Several aspects have been improved compared to NEMO-3: choice of the isotope, energy resolution, energy losses… but the main challenge is the background reduction. All the detector materials have been selected for their low natural radioactivity contaminations through High Purity Germanium (HPGe) gamma spectroscopy. The double beta sources after enrichment are being prepared with extreme care and the ultimate contaminations will be characterized by the most sensitive BiPo detector. External radon tightness and internal radon emanation have been studied to ensure a very low level in the tracker with very sensitive complementary detectors: diffusion apparatus, concentration line and emanation tanks. The construction of the first detector, called the demonstrator, has started in 2012. Studying 7 kg of {sup 82}Se, the demonstrator will reach the NEMO-3 sensitivity in only 5 months and improve it by at least a factor 6 in 2.5 years. Underground installation will start fall 2014 and physics data taking should start by summer 2015.
ISSN 0094243X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-07-15
Publisher Place United States
Volume Number 1666
Issue Number 1


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