The CUPID-Mo experiment, located at the Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20Li2Mo100O4 (LMO) calorimeters, each equipped with a Ge light detector for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double-β decays of Mo100 to the first 0+ and 2+ excited states of Ru100 using the full CUPID-Mo exposure (2.71kgyr of LMO). We measure the half-life of 2νββ decay to the 01+ state as T1/22ν→01+=(7.5±0.8(stat.)-0.3+0.4(syst.))×1020yr. The bolometric technique enables measurement of the electron energies as well as the γ rays from nuclear deexcitation and this allows us to set new limits on the two-neutrino decay to the 21+ state of T1/22ν→21+>4.4×1021yr(90% c.i.) and on the neutrinoless modes of T1/20ν→21+>2.1×1023yr(90% c.i.), T1/20ν→01+>1.2×1023yr(90% c.i.). Information on the electrons' spectral shape is obtained, which allows us to make the first comparison of the single and higher state dominance 2νββ decay models for the 01+ excited state of Ru100.

The CUPID-Mo experiment to search for 0$ u\beta\beta$ decay in $^{100}$Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0$ u\beta\beta$ decay experiment. CUPID-Mo was comprised of 20 enriched Li$_2$$^{100}$MoO$_4$ scintillating calorimeters, each with a mass of $\sim$ 0.2 kg, operated at $\sim$20 mK. We present here the final analysis with the full exposure of CUPID-Mo ($^{100}$Mo exposure of 1.47 kg$\times$yr) used to search for lepton number violation via 0$ u\beta\beta$ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the $^{100}$Mo 0$ u\beta\beta$ decay half-life of $T^{0 u}_{1/2} > 1.8 \times 10^{24}$ year (stat.+syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of $\left < (0.28$--$0.49)$ eV, dependent upon the nuclear matrix element utilized.

The CUPID-Mo experiment to search for 0νββ decay in 100Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0νββ decay experiment. CUPID-Mo was comprised of 20 enriched Li 2100MoO 4 scintillating calorimeters, each with a mass of ∼ 0.2 kg, operated at ∼ 20 mK. We present here the final analysis with the full exposure of CUPID-Mo (100Mo exposure of 1.47 kg × year) used to search for lepton number violation via 0νββ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the 100Mo 0νββ decay half-life of T1/20ν> 1.8 × 10 24 year (stat. + syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of 〈 mββ〉 <(0.28-0.49) eV, dependent upon the nuclear matrix element utilized.

CUPID-Mo, located in the Laboratoire Souterrain de Modane (France), was a demonstrator for the next generation 0 νββ decay experiment, CUPID. It consisted of an array of 20 enriched Li 2100 MoO 4 bolometers and 20 Ge light detectors and has demonstrated that the technology of scintillating bolometers with particle identification capabilities is mature. Furthermore, CUPID-Mo can inform and validate the background prediction for CUPID. In this paper, we present a detailed model of the CUPID-Mo backgrounds. This model is able to describe well the features of the experimental data and enables studies of the 2 νββ decay and other processes with high precision. We also measure the radio-purity of the Li 2100 MoO 4 crystals which are found to be sufficient for the CUPID goals. Finally, we also obtain a background index in the region of interest of 3.7 -0.8+0.9 (stat) -0.7+1.5 (syst) ×10-3 counts/ Δ EFWHM/ mol iso/ year , the lowest in a bolometric 0 νββ decay experiment.

The current experiments searching for neutrinoless double-β (0νββ) decay also collect large statistics of Standard Model allowed two-neutrino double-β (2νββ) decay events. These can be used to search for Beyond Standard Model (BSM) physics via 2νββ decay spectral distortions. 100Mo has a natural advantage due to its relatively short half-life, allowing higher 2νββ decay statistics at equal exposures compared to the other isotopes. We demonstrate the potential of the dual read-out bolometric technique exploiting a 100Mo exposure of 1.47 kg × years, acquired in the CUPID-Mo experiment at the Modane underground laboratory (France). We set limits on 0νββ decays with the emission of one or more Majorons, on 2νββ decay with Lorentz violation, and 2νββ decay with a sterile neutrino emission. In this analysis, we investigate the systematic uncertainty induced by modeling the 2νββ decay spectral shape parameterized through an improved model, an effect never considered before. This work motivates searches for BSM processes in the upcoming CUPID experiment, which will collect the largest amount of 2νββ decay events among the next-generation experiments.

CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay (0 νββ) of 100Mo. In this article, we detail the CUPID-Mo detector concept, assembly and installation in the Modane underground laboratory, providing results from the first datasets. The CUPID-Mo detector consists of an array of 20 100Mo -enriched 0.2 kg Li 2MoO 4 crystals operated as scintillating bolometers at ∼20mK. The Li 2MoO 4 crystals are complemented by 20 thin Ge optical bolometers to reject α events by the simultaneous detection of heat and scintillation light. We observe a good detector uniformity and an excellent energy resolution of 5.3 keV (6.5 keV) FWHM at 2615 keV, in calibration (physics) data. Light collection ensures the rejection of α particles at a level much higher than 99.9% – with equally high acceptance for γ/β events – in the region of interest for 100Mo 0 νββ. We present limits on the crystals’ radiopurity: ≤3μBq/kg of 226Ra and ≤2μBq/kg of 232Th. We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the 100Mo 0 νββ decay in half-a-year’s livetime. The achieved results show that CUPID-Mo is a successful demonstrator of the technology developed by the LUMINEU project and subsequently selected for the CUPID experiment, a proposed follow-up of CUORE, the currently running first tonne-scale bolometric 0 νββ experiment.

The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale bolometric 0νββ experiment. It consists of a 4.2 kg array of 20 enriched Li_{2}^{100}MoO_{4} scintillating bolometers to search for the lepton-number-violating process of 0νββ decay in ^{100}Mo. With more than one year of operation (^{100}Mo exposure of 1.17  kg×yr for physics data), no event in the region of interest and, hence, no evidence for 0νββ is observed. We report a new limit on the half-life of 0νββ decay in ^{100}Mo of T_{1/2}>1.5×10^{24}  yr at 90% C.I. The limit corresponds to an effective Majorana neutrino mass ⟨m_{ββ}⟩<(0.31-0.54)  eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.

We report the measurement of the two-neutrino double-beta (2 νββ) decay of 100Mo to the ground state of 100Ru using lithium molybdate (Li2100MoO4) scintillating bolometers. The detectors were developed for the CUPID-Mo program and operated at the EDELWEISS-III low background facility in the Modane underground laboratory (France). From a total exposure of 42.235 kg× day, the half-life of 100Mo is determined to be T1/22ν=[7.12-0.14+0.18(stat.)±0.10(syst.)]×1018 years. This is the most accurate determination of the 2 νββ half-life of 100Mo to date.

The CDMS and EDELWEISS collaborations have combined the results of their direct searches for dark matter using cryogenic germanium detectors. The total data set represents 614kg•days equivalent exposure. A straightforward method of combination was chosen for its simplicity before data were exchanged between experiments. The results are interpreted in terms of limits on spin-independent weakly interacting, massive particle (WIMP)-nucleon cross section. For a WIMP mass of 90GeV/c2, where this analysis is most sensitive, a cross section of 3.3×10-44cm2 is excluded at 90% C.L. At higher WIMP masses, the combination improves the individual limits, by a factor 1.6 above 700GeV/c2. Alternative methods of combining the data provide stronger constraints for some ranges of WIMP masses and weaker constraints for others. © 2011 American Physical Society.

This paper reports on the development of a technology involving 100Mo -enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ( ∼1kg ), high optical quality, radiopure 100Mo -containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2-0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q-value of the double-beta transition of 100Mo (3034 keV) is 4-6 keV FWHM. The rejection of the α -induced dominant background above 2.6 MeV is better than 8σ . Less than 10μBq/kg activity of 232Th(228Th) and 226Ra in the crystals is ensured by boule recrystallization. The potential of 100Mo -enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only 10kg×d exposure: the two neutrino double-beta decay half-life of 100Mo has been measured with the up-to-date highest accuracy as T1/2 = [6.90 ± 0.15(stat.) ± 0.37(syst.)] ×1018years . Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of 100Mo .