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1. Search for periodic modulations of the rate of double-β decay of 100Mo in the NEMO-3 detector

   https://doi.org/DOI: 10.1103/PhysRevC.104.L061601  

   R. Arnold, 1 C. (December 2021, Physical review and Physical review letters index)

   Double-beta decays of 100Mo from the 6.0195-year exposure of a 6.914 kg high-purity sample were recorded by the NEMO-3 experiment that searched for neutrinoless double-beta decays. These ultrarare transitions to 100Ru have a half-life of approximately 7 × 1018 years and have been used to conduct the first-ever search for periodic variations of this decay mode. The Lomb-Scargle periodogram technique, and its error-weighted extension, were employed to look for periodic modulations of the half-life. Data show no evidence at the 95% confidence level of modulations with amplitude greater than 2.5% in the frequency range of 0.33225 yr−1 to 360 yr−1. 

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2. Neutrinoless double β decay with light sterile neutrinos: the contact terms

   https://doi.org/10.1007/JHEP04(2025)181  

   Cirigliano, Vincenzo; Dekens, Wouter; Quiroga, Sebastián Urrutia (April 2025, Journal of High Energy Physics)

   A<sc>bstract</sc> We study neutrinoless double-beta decay in extensions of the Standard Model that includenright-handed neutrino singlets, with massesm_sbelow the GeV scale. Generalizing recently developed matching methods, we determine them_sdependence of the short-rangenn→ppcouplings that appear to leading order in the chiral effective field theory description of neutrinoless double beta decay. We focus on two scenarios, corresponding to the minimalνSM and left-right symmetric models. We illustrate the impact of our new results in the case of theνSM, showing a significant impact on the neutrinoless double-beta decay half-life whenm_sis in the 200–800 MeV range. 

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3. Relevance of the Nuclear Structure of the Stable Ge Isotopes to the Neutrino-less Double-Beta Decay of ⁷⁶ Ge

   https://doi.org/10.1051/epjconf/202023204011  

   Yates, S. W.; Peters, E. E.; Crider, B. P.; Mukhopadhyay, S.; Ramirez, A. P.; Mitchell, A.J.; Pavetich, S.; Koll, D. (January 2020, EPJ Web of Conferences)

   Gamma-ray detection following the inelastic neutron scattering reaction on isotopically enriched material was used to study the nuclear structure of 74 Ge. From these measurements, low-lying, low-spin excited states were characterized, new states and their decays were identified, level lifetimes were measured with the Doppler-shift attenuation method (DSAM), multipole mixing ratios were established, and transition probabilities were determined. New structural features in 74 Ge were identified, and the reanalysis of older 76 Ge data led to the placement of the 2 + member of the intruder band. In addition, a number of previously placed states in 74 Ge were shown not to exist. A procedure for future work, which will lead to meaningful data for constraining calculations of the neutrinoless double-beta decay matrix element, is suggested. 

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4. Search for double-beta decay of $$\mathrm {^{130}Te}$$ to the $$0^+$$ states of $$\mathrm {^{130}Xe}$$ with CUORE

   https://doi.org/10.1140/epjc/s10052-021-09317-z  

   Adams, D. Q.; Alduino, C.; Alfonso, K.; Avignone, F. T.; Azzolini, O.; Bari, G.; Bellini, F.; Benato, G.; Biassoni, M.; Branca, A.; et al (July 2021, The European Physical Journal C)

   null (Ed.)

   Abstract The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ( $$0\nu \beta \beta $$ 0 ν β β ) in the isotope $$\mathrm {^{130}Te}$$ 130 Te . In this work we present the latest results on two searches for the double beta decay (DBD) of $$\mathrm {^{130}Te}$$ 130 Te to the first $$0^{+}_2$$ 0 2 + excited state of $$\mathrm {^{130}Xe}$$ 130 Xe : the $$0\nu \beta \beta $$ 0 ν β β decay and the Standard Model-allowed two-neutrinos double beta decay ( $$2\nu \beta \beta $$ 2 ν β β ). Both searches are based on a 372.5 kg $$\times $$ × yr TeO $$_2$$ 2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as $$\mathrm {S^{0\nu }_{1/2} = 5.6 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 0 ν = 5.6 × 10 24 yr for the $${0\nu \beta \beta }$$ 0 ν β β decay and $$\mathrm {S^{2\nu }_{1/2} = 2.1 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 2 ν = 2.1 × 10 24 yr for the $${2\nu \beta \beta }$$ 2 ν β β decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at $$90\%$$ 90 % C.I. on the decay half lives is obtained as: $$\mathrm {(T_{1/2})^{0\nu }_{0^+_2} > 5.9 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 0 ν > 5.9 × 10 24 yr for the $$0\nu \beta \beta $$ 0 ν β β mode and $$\mathrm {(T_{1/2})^{2\nu }_{0^+_2} > 1.3 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 2 ν > 1.3 × 10 24 yr for the $$2\nu \beta \beta $$ 2 ν β β mode. These represent the most stringent limits on the DBD of $$^{130}$$ 130 Te to excited states and improve by a factor $$\sim 5$$ ∼ 5 the previous results on this process. 

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5. Observation of two-neutrino double electron capture in 124Xe with XENON1T

   https://doi.org/10.1038/s41586-019-1124-4  

   E. Aprile, 1J. Aalbers (April 2019, Nature)

   Two-neutrino double electron capture (2νECEC) is a second-order Weak process with predictedhalf-lives that surpass the age of the Universe by many orders of magnitude [1]. Until now, indi-cations for 2νECEC decays have only been seen for two isotopes,78Kr [2, 3] and130Ba [4, 5], andinstruments with very low background levels are needed to detect them directly with high statisticalsignificance [6, 7]. The 2νECEC half-life provides an important input for nuclear structure models[8–14] and its measurement represents a first step in the search for the neutrinoless double electroncapture processes (0νECEC). A detection of the latter would have implications for the nature of theneutrino and give access to the absolute neutrino mass [15–17]. Here we report on the first directobservation of 2νECEC in124Xe with the XENON1T Dark Matter detector. The significance of thesignal is 4.4σand the corresponding half-lifeT2νECEC1/2= (1.8±0.5stat±0.1sys)×1022y is the longestever measured directly. This study demonstrates that the low background and large target massof xenon-based Dark Matter detectors make them well suited to measuring other rare processes aswell, and it highlights the broad physics reach for even larger next-generation experiments 

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