Final results on the $$0\nu \beta \beta $$ decay half-life limit of $$^{100}$$Mo from the CUPID-Mo experiment

Abstract

The CUPID-Mo experiment to search for 0$$\nu \beta \beta $$ ν β β decay in $$^{100}$$ 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$$\nu \beta \beta $$ ν β β decay experiment. CUPID-Mo was comprised of 20 enriched $$\hbox {Li}_{{2}}$$ Li 2 $$^{100}$$ 100 $$\hbox {MoO}_4$$ MoO 4 scintillating calorimeters, each with a mass of $$\sim 0.2$$ ∼ 0.2 kg, operated at $$\sim 20$$ ∼ 20 mK. We present here the final analysis with the full exposure of CUPID-Mo ($$^{100}$$ 100 Mo exposure of 1.47 $$\hbox {kg} \times \hbox {year}$$ kg × year ) used to search for lepton number violation via 0$$\nu \beta \beta $$ ν β β 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 $$^{100}$$ 100 Mo 0$$\nu \beta \beta $$ ν β β decay half-life of $$T_{1/2}^{0\nu }$$ T 1 / 2 0 ν $$> {1.8}\times 10^{24}$$ > 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 $$\left<m_{\beta \beta }\right>$$ m β β $$<~{(0.28{-}0.49)} $$ < ( 0.28 - 0.49 ) eV, dependent upon the nuclear matrix element utilized.

New measurement of double- β decays of Mo100 to excited states of Ru100 with the

“…Most of the data processing steps are the same as described in Refs. [31,47]. An optimal trigger is used to identify physics events and an optimal filter which maximizes the signal-to-noise ratio is used to compute amplitudes (both LD and LMO detectors) [60].…”

“…decay events with very low background. We define the multiplicity M as the number of crystals subject to simultaneous energy depositions above the analysis energy threshold, chosen as 40 keV, well above the detector trigger thresholds and within a time window of ±10 ms well above the detector time resolution [31].…”

“…The difference to the HSD model is then treated as a systematic uncertainty. We combine the MC simulations with inputs from experimental data to reproduce the detector response of each individual detector, accounting for (i) the energy threshold (set at 40 keV) [31]; (ii) the multiplicity of events; (iii) the energy resolution of each detector-dataset pair (energy dependent); (iv) the rejected periods of detector operations due to periods of cryogenic instability (i.e., due to environmental disturbances); (v) scintillation light, light-detector energy resolution, and cuts based on the LDs (see Sec. IV).…”

“…At present the upper limit on the effective Majorana mass m ββ ranges from 60 to 600 meV [8,12,[28][29][30]. Despite its low exposure, CUPID-Mo has set the most stringent limit on 0νββ decay in 100 Mo, with T 0ν 1/2 > 1.8 × 10 24 yr or m ββ < (0.28-0.49) eV [31].…”

Preparation of low-radioactive high-purity enriched 100MoO3 powder for AMoRE-II experiment

“…40 (17) keV [4], while most natural gamma radiation has energies below 2615 keV. However, searching for the 0νDBD is challenging because of the long half-lives, greater than 1.1 × 10 24 yr for 100 Mo [5,6]. This limit corresponds to ~5.5 count/kg•year, while the next generation of the 0νDBD experiments aims to probe the 10 26 -10 27 years half-live range [7].…”