#
Recent Developments and Results on Double Beta Decays with Crystal Scintillators and HPGe Spectrometry^{ †}

^{1}

^{2}

^{3}

^{4}

^{5}

^{6}

^{7}

^{8}

^{9}

^{10}

^{11}

^{12}

^{13}

^{*}

^{†}

## Abstract

**:**

## 1. Introduction

## 2. Observation of $2\nu 2\beta $ Decay of ${}^{100}$Mo in the ARMONIA Experiment

## 3. Search for Double Beta Decay in ${}^{116}$Cd with the AURORA Experiment

## 4. Search for Double Beta Decay in ${}^{106}$Cd with the DAMA/CRYS Setup

## 5. Preliminary Results for ${}^{150}$Nd 2$\beta $ Decay with the GeMulti Setup

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Bernabei, R.; Belli, P.; Bussolotti, A.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Dai, C.J.; d’Angelo, A.; Di Marco, A.; He, H.L.; et al. First model independent results from DAMA/LIBRA–phase2. Universe
**2018**, 4, 116. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Boiko, R.S.; Cappella, F.; Cerulli, R.; Danevich, F.A.; d’Angelo, S.; Incicchitti, A.; Kobychev, V.V.; Kropivyansky, B.N.; et al. New observation of 2β2ν decay of
^{100}Mo to the 0${}_{1}^{+}$ level of^{100}Ru in the ARMONIA experiment. Nucl. Phys. A**2010**, 846, 143–156. [Google Scholar] [CrossRef] - Polischuk, O.G.; Barabash, A.S.; Belli, P.; Bernabei, R.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D.M.; Danevich, F.A.; d’Angelo, S.; et al. Investigation of 2β decay of
^{116}Cd with the help of enriched^{116}CdWO_{4}crystal scintillators. AIP Conf. Proc.**2017**, 1894, 020018. [Google Scholar] [CrossRef] - Barabash, A.S.; Belli, P.; Bernabei, R.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Danevich, F.A.; Di Marco, A.; Incicchitti, A.; Kasperovych, R.V.; et al. Double beta decay of
^{150}Nd to the first excited 0^{+}level of^{150}Sm: Preliminary results. Nucl. Phys. At. Energy**2018**, 19, 95–102. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Dai, C.J.; Danevich, F.A.; d’Angelo, A.; Incicchitti, A.; Kobychev, V.V.; Nagorny, S.S.; et al. Search for α decay of natural Europium. Nucl. Phys. A
**2007**, 789, 15–29. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F.A.; Incicchitti, A.; Laubenstein, M.; Nagorny, S.S.; Nisi, S.; Polischuk, O.G.; et al. First observation of α decay of
^{190}Pt to the first excited level (E_{exc}= 137.2 keV) of^{186}Os. Phys. Rev. C**2011**, 83, 034603. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Bukilic, N.; Cappella, F.; Cerulli, R.; Dai, C.J.; Danevich, F.A.; de Laeter, J.R.; Incicchitti, A.; Kobychev, V.V.; et al. Investigation of β decay of
^{113}Cd. Phys. Rev. C**2007**, 76, 064603. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cappella, F.; Cerulli, R.; Montecchia, F.; Nozzoli, F.; Incicchitti, A.; Prosperi, D.; Tretyak, V.I.; Zdesenko, Y.G.; et al. Search for β and ββ decays in
^{48}Ca. Nucl. Phys. A**2002**, 705, 29–39. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cappella, F.; Caracciolo, V.; Castellano, S.; Cerulli, R.; Dai, C.J.; d’Angelo, A.; Di Marco, A.; He, H.L.; et al. New search for correlated e
^{+}e^{−}pairs in the α decay of^{241}Am. Eur. Phys. J. A**2013**, 49, 64. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cerulli, R.; Montecchia, F.; Nozzoli, F.; Incicchitti, A.; Prosperi, D.; Dai, C.J.; He, H.L.; Kuang, H.H.; et al. Search for solar axions by Primakoff effect in NaI crystals. Phys. Lett. B
**2001**, 515, 6–12. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F.A.; d’Angelo, A.; Incicchitti, A.; Kobychev, V.V.; Laubenstein, M.; Polischuk, O.G.; et al. Search for
^{7}Li solar axions using resonant absorption in LiF crystal: Final results. Phys. Lett. B**2012**, 711, 41–45. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Cerulli, R.; Danevich, F.A.; d’Angelo, A.; Goriletski, V.I.; Grinvov, B.V.; Incicchitti, A.; Kobychev, V.V.; Laubenstein, M.; et al.
^{7}Li solar axions: Preliminary results and feasibility studies. Nucl. Phys. A**2008**, 806, 388–397. [Google Scholar] [CrossRef] - Cappella, F.; Cerulli, R.; Incicchitti, A. A preliminary search for Q-balls by delayed coincidences in NaI(Tl). Eur. Phys. J. direct C
**2002**, 14, 1–6. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cerulli, R.; Montecchia, F.; Amato, M.; Ignesti, G.; Icicchitti, A.; Prosperi, D.; Dai, C.J.; He, H.L.; et al. Extended Limits on Neutral Strongly Interacting Massive Particles and Nuclearites from NaI(Tl) Scintillators. Phys. Rev. Lett.
**1999**, 83, 4918. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cappella, F.; Cerulli, R.; d’Angelo, A.; Emiliani, F.; Incicchitti, A. Search for Daemons with NEMESIS. Mod. Phys. Lett. A
**2012**, 27, 1250031. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Dai, C.J.; He, H.L.; Ignesti, G.; Icicchitti, A.; Kuang, H.H.; Ma, J.M.; Montecchia, F.; Ponkratenko, O.A.; et al. New experimental limit on the electron stability and non-paulian transitions in Iodine atoms. Phys. Lett. B
**1999**, 460, 236–241. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Di Nicolantonio, W.; Landoni, V.; Incicchitti, A.; Prosperi, D.; Dai, C.J.; Bacci, C. Charge conservation and electron lifetime: Limits from a liquid xenon scintillator. Astrop. Phys.
**1996**, 5, 217–219. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Dai, C.J.; Ignesti, G.; Icicchitti, A.; Montecchia, F.; Ponkratenko, O.A.; Prosperi, D.; Tretyak, V.I.; Zdesenko, Y.G. Quest for electron decay e
^{−}→ ν_{e}γ with a liquid xenon scintillator. Phys. Rev. D**2000**, 61, 117301. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cappella, F.; Montecchia, F.; Nozzoli, F.; d’Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C.J.; et al. Search for spontaneous transition of nuclei to a superdense state. Eur. Phys. J. A
**2005**, 23, 7–10. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cappella, F.; Montecchia, F.; Nozzoli, F.; d’Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C.J.; et al. A search for spontaneous emission of heavy clusters in the
^{127}I nuclide. Eur. Phys. J. A**2005**, 24, 51–56. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Montecchia, F.; Nozzoli, F.; d’Angelo, A.; Cappella, F.; Incicchitti, A.; Prosperi, D.; Castellano, S.; Cerulli, R.; et al. Performances and potentialities of a LaCl
_{3}: Ce scintillator. Nucl. Instr. Meth. A**2005**, 555, 270–281. [Google Scholar] [CrossRef] - Bernabei, R.; Amato, M.; Belli, P.; Cerulli, R.; Dai, C.J.; Denisov, V.Y.; He, H.L.; Incicchitti, A.; Kuang, H.H.; Ma, J.M.; et al. Search for the nucleon and di-nucleon decay into invisible channels. Phys. Lett. B
**2000**, 493, 12–18. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C.J.; Denisov, V.Y.; et al. Search for rare processes with DAMA/LXe experiment at Gran Sasso. Eur. Phys. J. A
**2006**, 27, 35–41. [Google Scholar] [CrossRef] [Green Version] - Bernabei, R.; Belli, P.; Cappella, F.; Cerulli, R.; Dai, C.J.; d’Angelo, A.; d’Angelo, S.; Di Marco, A.; He, H.L.; Incicchitti, A.; et al. Search for charge non-conserving processes in
^{127}I by coincidence technique. Eur. Phys. J. C**2012**, 72, 1920. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Montecchia, F.; Nozzoli, F.; d’Angelo, A.; Capella, F.; Incicchitti, A.; Prosperi, D.; Castellano, S.; Cerulli, R.; et al. Search for possible charge non-conserving decay of
^{139}La into^{139}Ce with LaCl_{3}(Ce) scintillator. Ukr. J. Phys.**2006**, 51, 1037–1043. [Google Scholar] - Belli, P.; Bernabei, R.; Dai, C.J.; He, H.L.; Ignesti, G.; Incicchitti, A.; Kuang, H.H.; Ma, J.M.; Montecchia, F.; Ponkratenko, O.A.; et al. New limits on the nuclear levels excitation of
^{127}I and^{23}Na during charge nonconservation. Phys. Rev. C**1999**, 60, 065501. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Dai, C.J.; Ignesti, G.; Incicchitti, A.; Montecchia, F.; Ponkratenko, O.A.; Prosperi, D.; Tretyak, V.I.; Zdesenko, Y.G. Charge non-conservation restrictions from the nuclear levels excitation of
^{129}Xe induced by the electron’s decay on the atomic shell. Phys. Lett. B**1999**, 465, 315–322. [Google Scholar] [CrossRef] - Bernabei, R.; Belli, P.; Cappella, F.; Cerulli, R.; Dai, C.J.; d’Angelo, A.; He, H.L.; Incicchitti, A.; Kuang, H.H.; Ma, J.M.; et al. New search for processes violating the Pauli exclusion principle in sodium and in iodine. Eur. Phys. J. C
**2009**, 62, 327–332. [Google Scholar] [CrossRef] [Green Version] - Bernabei, R.; Belli, P.; Montecchia, F.; de Sanctis, M.; di Nicolantonio, W.; Incicchitti, A.; Prosperi, D.; Bacci, C.; Dai, C.J.; Ding, L.K.; et al. Search for non-paulian transitions in
^{23}Na and^{127}I. Phys. Lett. B**1997**, 408, 439–444. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Danevich, F.A.; Di Marco, A.; Incicchitti, A.; Poda, D.V.; Polischuk, O.G.; et al. Investigation of rare nuclear decays with BaF
_{2}crystal scintillator contaminated by radium. Eur. Phys. J. A**2014**, 50, 134. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Cappella, F.; Cerulli, R.; Danevich, F.A.; Denisov, V.Y.; d’Angelo, A.; Incicchitti, A.; Kobychev, V.V.; Poda, D.V.; et al. Search for long-lived superheavy eka-tungsten with radiopure ZnWO
_{4}crystal scintillator. Phys. Scr.**2015**, 90, 085301. [Google Scholar] [CrossRef] - Tretyak, V.I.; Zdesenko, V.I. Tables of double beta decay data-an update. Atom. Data Nucl. Data
**2002**, 80, 83–116. [Google Scholar] [CrossRef] - Meija, J.; Coplen, T.B.; Berglund, M.; Brand, W.A.; De Bièvre, P.; Gröning, M.; Holden, N.E.; Irrgeher, J.; Loss, R.D.; Walczyk, T.; et al. Isotopic compositions of the elements 2013 (IUPAC Technical Report). Pure Appl. Chem.
**2016**, 88, 293–306. [Google Scholar] [CrossRef] [Green Version] - Wang, M.; Audi, G.; Kondev, F.G.; Huang, W.J.; Naimi, S.; Xu, X. The AME2016 atomic mass evaluation (II). Tables, graphs and references. Chin. Phys. C
**2017**, 41, 030003. [Google Scholar] [CrossRef] - Hidaka, H.; Ly, C.V.; Suzuki, M. Geochemical evidence of the double β decay of
^{100}Mo. Phys. Rev. C**2004**, 70, 025501. [Google Scholar] [CrossRef] - Barabash, A.S. Average and recommended half-life values for two-neutrino double beta decay. Nucl. Phys. A
**2015**, 935, 52–64. [Google Scholar] [CrossRef] [Green Version] - Armengaud, E.; Augier, C.; Barabash, A.S.; Beeman, J.W.; Bekker, T.B.; Bellini, F.; Benoît, A.; Bergé, L.; Bergmann, T.; Billard, J.; et al. Development of
^{100}Mo-containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search. Eur. Phys. J. C**2017**, 77, 785. [Google Scholar] [CrossRef] - Barabash, A.S.; Avignone, F.T., III; Collar, J.I.; Guerard, C.K.; Arthur, R.J.; Brodzinski, R.L.; Miley, H.S.; Reeves, J.H.; Meier, J.R.; Ruddick, K.; et al. Two neutrino double-beta decay of
^{100}Mo to the first excited 0^{+}state in^{100}Ru. Phys. Lett. B**1995**, 345, 408–413. [Google Scholar] [CrossRef] - Barabash, A.S.; Avignone, F.T., III; Guerard, C.K.; Brodzinski, R.L.; Miley, H.S.; Reeves, J.H.; Umatov, V.I. Proceedings of the 26th Rencontre de Moriond: Festschrift Wuthrick (JP)-11th Moriond Workshop Massive Neutrinos Test of Fundamental Symmetries. 1991; p. 77. Available online: https://cds.cern.ch/record/227770/files/C91-01-26_Proceedings.pdf (accessed on 12 December 2018).
- Barabash, A.S.; Avignone, F.T., III; Guerard, C.K.; Brodzinski, R.L.; Miley, H.S.; Reeves, J.H.; Umatov, V.I. Two neutrino double-beta decay of 100Mo to the first excited 0+ state in 100Ru. In Proceedings of the 3rd International Symposium WEIN’92, Dubna, Russia, 16–22 June 1992; World Scientific: Singapore, 1993; p. 582. [Google Scholar]
- Barabash, A.S.; Gurriaran, R.; Hubert, F.; Hubert, P.; Umatov, V.I. 2νββ decay of
^{100}Mo to the first 0^{+}excited state in^{100}Ru. Phys. At. Nucl.**1999**, 62, 2039–2043. [Google Scholar] - Arnold, R.; Augier, C.; Baker, J.; Barabash, A.S.; Bongrand, M.; Broudin, G.; Brudanin, V.; Caffrey, A.J.; Egorov, V.; Etienvre, A.I.; et al. Measurement of double beta decay of
^{100}Mo to excited states in the NEMO 3 experiment. Nucl. Phys. A**2007**, 781, 209–226. [Google Scholar] [CrossRef] - Kidd, M.F.; Esterline, J.H.; Tornow, W.; Barabash, A.S.; Umatov, V.I. New results for double-beta decay of
^{100}Mo to excited final states of^{100}Ru using the TUNL-ITEP apparatus. Nucl. Phys. A**2009**, 821, 251–261. [Google Scholar] [CrossRef] - De Braeckeleer, L.; Hornish, M.; Barabash, A.S.; Umatov, V.I. Measurement of the ββ-Decay Rate of
^{100}Mo to the First Excited 0^{+}State of^{100}Ru. Phys. Rev. Lett.**2001**, 86, 3510. [Google Scholar] [CrossRef] [PubMed] - Hornish, M.J.; De Braeckeleer, L.; Barabash, A.S.; Umatov, V.I. Double β decay of
^{100}Mo to excited final states. Phys. Rev. C**2006**, 74, 044314. [Google Scholar] [CrossRef] - Arnold, R.; Augier, C.; Barabash, A.S.; Basharina-Freshville, A.; Blondel, S.; Blot, S.; Bongrand, M.; Brudanin, V.; Busto, J.; Caffrey, A.J.; et al. Investigation of double beta decay of
^{100}Mo to excited states of^{100}Ru. Nucl. Phys. A**2014**, 925, 25–36. [Google Scholar] [CrossRef] - Blum, D.; Bust, J.; Campagne, J.E.; Dassié, D.; Hubert, F.; Hubert, P.; Isaac, M.C.; Izac, C.; Jullian, S.; Kouts, B.N.; et al. Search for γ-rays following ββ decay of
^{100}Mo to excited states of^{100}Ru. Phys. Lett. B**1992**, 275, 506–511. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Boiko, R.S.; Cerulli, R.; Danevich, F.A.; d’Angelo, S.; Incicchitti, A.; Kobychev, V.V.; Kropivyansky, B.N.; Laubenstein, M.; et al. Preliminary results on the search for
^{100}Mo 2β decay to the first excited 0${}_{1}^{+}$ level of^{100}Ru. In Proceedings of the International Conference “Current Problems in Nuclear Physics and Atomic Energy“, Kyiv, Ukraine, 29 May–3 June 2006; pp. 479–482. [Google Scholar] - Belli, P.; Bernabei, R.; Boiko, R.S.; Cappella, F.; Cerulli, R.; Danevich, F.A.; d’Angelo, S.; Incicchitti, A.; Kobychev, V.V.; Kropivyansky, B.N.; et al. Preliminary results on the search for 100Mo 2β decay to the first excited 0${}_{1}^{+}$, level of
^{100}Ru (ARMONIA Experiment). In Proceedings of the International Conference Current Problems in Nuclear Physics and Atomic Energy, Kyiv, Ukraine, 29 May–3 June 2006; pp. 473–476. [Google Scholar] - Nelson, W.R.; Hirayama, H.; Rogers, D.W.O. The EGS4 CODE SYSTEM; Technical report SLAC-265; Stanford Linear Accelerator Center Stanford University: Stanford, CA, USA, 1985. [Google Scholar]
- Agostinelli, S.; Allison, J.; Amako, K.; Apostolakis, J.; Araujo, H.; Arce, P.; Asai, M.; Axen, D.; Banerjee, S.; Barrand, G.; et al. Geant4-a simulation toolkit. Nucl. Instrum. Meth. A
**2003**, 506, 250–303. [Google Scholar] [CrossRef] - Rodryguez, T.R.; Martynez-Pinedo, G. Energy Density Functional Study of Nuclear Matrix Elements for Neutrinoless ββ Decay. Phys. Rev. Lett.
**2010**, 105, 252503. [Google Scholar] [CrossRef] - Simkovic, F.; Rodin, V.; Faessler, A.; Vogel, P. 0νββ and 2νββ nuclear matrix elements, quasiparticle random-phase approximation, and isospin symmetry restoration. Phys. Rev. C
**2013**, 87, 045501. [Google Scholar] [CrossRef] - Hyvarinen, J.; Suhonen, J. Nuclear matrix elements for 0νββ decays with light or heavy Majorana-neutrino exchange. Phys. Rev. C
**2015**, 91, 024613. [Google Scholar] [CrossRef] - Barea, J.; Kotila, J.; Iachello, F. 0νββ and 2νββ nuclear matrix elements in the interacting boson model with isospin restoration. Phys. Rev. C
**2015**, 91, 034304. [Google Scholar] [CrossRef] - Barabash, A.S.; Belli, P.; Bernabei, R.; Boiko, R.S.; Cappella, F.; Caracciolo, V.; Chernyak, D.M.; Cerulli, R.; Danevich, F.A.; Di Vacri, M.L.; et al. Low background detector with enriched
^{116}CdWO_{4}crystal scintillators to search for double β decay of^{116}Cd. JINST**2011**, 6, P08011. [Google Scholar] [CrossRef] - Barabash, A.S.; Belli, P.; Bernabei, R.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D.M.; Danevich, F.A.; d’Angelo, S.; Incicchitti, A.; et al. Final results of the Aurora experiment to study 2β decay of
^{116}Cd with enriched^{116}CdWO_{4}crystal scintillators. Phys. Rev. D**2018**, 98, 092007. [Google Scholar] [CrossRef] - Gatti, E.; De Martini, F. A new linear method of discrimination between elementary particles in scintillation counters. In Nuclear Electronics II, Proceedings of the Conference on Nuclear Electronics, V.II, Belgrade, Yugoslavia, 15–20 May 1961; Brüder Rosenbaum: Vienna, Austria, 1962; pp. 265–276. [Google Scholar]
- Bardelli, L.; Bini, M.; Bizzeti, P.G.; Carraresi, L.; Danevich, F.A.; Fazzini, T.F.; Grinyov, B.V.; Ivannikova, N.V.; Kobychev, V.V.; Kropivyansky, B.N.; et al. Further study of CdWO
_{4}crystal scintillators as detectors for high sensitivity 2β experiments: Scintillation properties and pulse-shape discrimination. Nucl. Instr. Meth. A**2006**, 569, 743–753. [Google Scholar] [CrossRef] - Danevich, F.A.; Kobychev, V.V.; Ponkratenko, O.A.; Tretyak, V.I.; Zdesenko, Y.G. Quest for double beta decay of
^{160}Gd and Ce isotopes. Nucl. Phys. A**2001**, 694, 375–391. [Google Scholar] [CrossRef] - Ponkratenko, O.A.; Tretyak, V.I.; Zdesenko, Y.G. Event generator DECAY4 for simulating double-beta processes and decays of radioactive nuclei. Phys. At. Nucl.
**2000**, 63. [Google Scholar] [CrossRef] - Feldman, G.J.; Cousins, R.D. Unified approach to the classical statistical analysis of small signals. Phys. Rev. D
**1998**, 57, 3873. [Google Scholar] [CrossRef] - Kotila, J.; Iachello, F. Phase-space factors for double-β decay. Phys. Rev. C
**2012**, 85, 034316. [Google Scholar] [CrossRef] - Meshik, A.P.; Hohenberg, C.M.; Pravdivtseva, O.V.; Kapusta, Y.S. Weak decay of
^{130}Ba and^{132}Ba: Geochemical measurements. Phys. Rev. C**2001**, 64, 035205. [Google Scholar] [CrossRef] - Pujol, M.; Marty, B.; Burnard, P.; Philippot, P. Xenon in Archean barite: Weak decay of
^{130}Ba, mass-dependent isotopic fractionation and implication for barite formation. Geochim. Cosmochim. Acta**2009**, 73, 6834–6846. [Google Scholar] [CrossRef] - Gavrilyuk, Y.M.; Gangapshev, A.M.; Kazalov, V.V.; Kuzminov, V.V.; Panasenko, S.I.; Ratkevich, S.S. Indications of 2ν2K capture in
^{78}Kr. Phys. Rev. C**2013**, 87, 035501. [Google Scholar] [CrossRef] - Ratkevich, S.S.; Gangapshev, A.M.; Gavrilyuk, Y.M.; Karpeshin, F.F.; Kazalov, V.V.; Kuzminov, V.V.; Panasenko, S.I.; Trzhaskovskaya, M.B.; Yakimenko, S.P. Comparative study of the double-K-shell-vacancy production in single- and double-electron-capture decay. Phys. Rev. C
**2017**, 96, 065502. [Google Scholar] [CrossRef] - Hirsch, M.; Muto, K.; Oda, T.; Klapdor-Kleingrothaus, H.V. Nuclear structure calculation of β
^{+}β^{+}, β^{+}/EC and EC/EC decay matrix elements. Z. Phys. A**1994**, 347, 151–160. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Boiko, R.S.; Brudanin, V.B.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D.M.; Danevich, F.A.; d’Angelo, S.; et al. Search for double-β decay processes in
^{106}Cd with the help of a^{106}CdWO_{4}crystal scintillator. Phys. Rev. C**2012**, 85, 044610. [Google Scholar] [CrossRef] - Krivoruchenko, M.I.; Šimkovic, F.; Frekerse, D.; Faessler, A. Resonance enhancement of neutrinoless double electron capture. Nucl. Phys. A
**2011**, 859, 140–171. [Google Scholar] [CrossRef] - Belli, P.; Bernabei, R.; Brudanin, V.B.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D.M.; Danevich, F.A.; d’Angelo, S.; Di Marco, A.; et al. Search for 2β decay of
^{106}Cd with an enriched^{106}CdWO_{4}crystal scintillator in coincidence with four HPGe detectors. Phys. Rev. C**2016**, 93, 045502. [Google Scholar] [CrossRef] - Boiko, R.S.; Virich, V.D.; Danevich, F.A.; Dovbush, T.I.; Kovtun, G.P.; Nagornyi, S.S.; Nisi, S.; Samchuk, A.I.; Solopikhin, D.A.; Shcherban’, A.P. Ultrapurification of archaeological lead. Inorg. Mater.
**2011**, 47, 645–648. [Google Scholar] [CrossRef] - Danevich, F.A.; Kim, S.K.; Kim, H.J.; Kim, Y.D.; Kobychev, V.V.; Kostezh, A.B.; Kropivyansky, B.N.; Laubenstein, M.; Mokina, V.M.; Nagorny, S.S.; et al. Ancient Greek lead findings in Ukraine. Nucl. Instr. Meth. A
**2009**, 603, 328–332. [Google Scholar] [CrossRef] - Danevich, F.A.; Georgadze, A.S.; Kobychev, V.V.; Kropivyansky, B.N.; Kuts, V.N.; Nikolaiko, A.S.; Tretyak, V.I.; Zdesenko, Y. The research of 2β decay of
^{116}Cd with enriched^{116}CdWO_{4}crystal scintillators. Phys. Lett. B**1995**, 344, 72–78. [Google Scholar] [CrossRef] - Artemiev, V.; Brakchmana, E.; Karelina, K.; Kirichenko, V.; Klimenko, A.; Kozodaeva, O.; Lubimov, A.; Mitin, A.; Osetrov, S.; Paramokhin, V.; et al. Half-life measurement of
^{150}Nd 2β2ν decay in the time projection chamber experiment. Phys. Lett. B**1995**, 345, 564–568. [Google Scholar] [CrossRef] - De Silva, A.; Moe, M.K.; Nelson, M.A.; Vient, M.A. Double β decays of
^{100}Mo and^{150}Nd. Phys. Rev. C**1997**, 56, 2541. [Google Scholar] [CrossRef] - Arnold, R.; Augier, C.; Baker, J.D.; Barabash, A.S.; Basharina-Freshville, A.; Blondel, S.; Blot, S.; Bongrand, M.; Brudanin, V.; Busto, J.; et al. The NEMO-3 Collaboration Measurement of the 2νββ decay half-life of
^{150}Nd and a search for 0νββ decay processes with the full exposure from the NEMO-3 detector. Phys. Rev. D**2016**, 94, 072003. [Google Scholar] [CrossRef] - Barabash, A.S.; Hubert, F.; Hubert, P.; Umatov, V.I. Double beta decay of
^{150}Nd to the first 0^{+}excited state of^{150}Sm. JETP Lett.**2004**, 79, 10–12. [Google Scholar] [CrossRef] - Barabash, A.S.; Hubert, P.; Nachab, A.; Umatov, V.I. Investigation of ββ decay in
^{150}Nd and^{148}Nd to the excited states of daughter nuclei. Phys. Rev. C**2009**, 79, 045501. [Google Scholar] [CrossRef] - Kidd, M.F.; Esterline, J.H.; Finch, S.W.; Tornow, W. Two-neutrino double-β decay of
^{150}Nd to excited final states in^{150}Sm. Phys. Rev. C**2014**, 90, 055501. [Google Scholar] [CrossRef]

1. | DAMA operates several low-background setups at LNGS: DAMA/NaI (out of operation in 2002), DAMA/LIBRA, DAMA/R&D, DAMA/CRYS, DAMA/LXe (out of operation in 2018), DAMA/Ge, and other HPGe detectors from the STELLA facility. |

**Figure 1.**

**Left**: (Color on-line) Energy spectrum collected with the ${}^{100}$MoO${}_{3}$ sample (points with error bars) in the (490–630) keV energy region, together with the fit (continuous curve). The background spectrum (normalized to 18120 h) is also shown (filled-in histogram). Both the 540 and 591 keV peaks of the $2\nu 2\beta $ decay ${}^{100}$Mo → ${}^{100}$Ru$\left({0}_{1}^{+}\right)$ are clearly visible in the energy spectrum of the ${}^{100}$MoO${}_{3}$ sample.

**Right**: (Color on-line) The coincidence energy spectra accumulated over a period of 17807 h with the ${}^{100}$MoO${}_{3}$ sample in the four-HPGe setup when the energy of one detector was fixed at the value expected for the ${}^{100}$Mo → ${}^{100}$Ru$\left({0}_{1}^{+}\right)$ $2\nu 2\beta $ decay: ($540\pm 2$) keV (top) and ($591\pm 2$) keV (middle). The bottom figure shows the background obtained by shifting the energy of one detector to ($545\pm 2$) keV.

**Figure 2.**Energy spectrum of $\gamma \left(\beta \right)$ events collected by the ${}^{116}$CdWO${}_{4}$ detectors in the region of interest for $2\nu 2\beta $ decay (on the left, T = 26831 h) and $0\nu 2\beta $ decay (on the right, T = 35324 h) of ${}^{116}$Cd. Also shown are the main components of the background model: the $2\nu 2\beta $ decay of ${}^{116}$Cd, the internal contamination of the ${}^{116}$CdWO${}_{4}$ crystals by U/Th, K (“int. U“, “int. Th“, “${}^{40}$K“) and contributions from external $\gamma $s (“ext. $\gamma $” or “ext. Th.“). The peak of the $0\nu 2\beta $ decay of ${}^{116}$Cd excluded at 90% C.L. is also shown.

**Figure 3.**Schematic view of the ${}^{106}$CdWO${}_{4}$ setup that is now running in the DAMA/CRYS setup at LNGS.

**Figure 4.**Coincidence energy spectra measured by the GeMulti setup with the 2.381 kg Nd${}_{2}$O${}_{3}$ sample over 16,375 h when the energy in one detector was fixed to the energy interval at which $\gamma $s from the ${}^{150}$Nd → ${}^{150}$Sm (0${}_{1}^{+}$, 740.5 keV) decay—406.5 keV ± 1.4 × FWHM (top), 334.0 keV ± 1.4 × FWHM (middle)—are expected. The bottom spectrum shows a random coincidence background in the energy range of interest when the energy of events in one of the detectors is taken as 375 keV ± 1.4 × FWHM (no $\gamma $s with this energy are expected in either the ${}^{150}$Nd 2$\beta $ decay nor in the decays of nuclides that are radioactive contaminants of the Nd${}_{2}$O${}_{3}$ sample or of the setup).

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Di Marco, A.; Barabash, A.S.; Belli, P.; Bernabei, R.; Boiko, R.S.; Brudanin, V.B.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Chernyak, D.M.;
et al. Recent Developments and Results on Double Beta Decays with Crystal Scintillators and HPGe Spectrometry. *Universe* **2018**, *4*, 147.
https://doi.org/10.3390/universe4120147

**AMA Style**

Di Marco A, Barabash AS, Belli P, Bernabei R, Boiko RS, Brudanin VB, Cappella F, Caracciolo V, Cerulli R, Chernyak DM,
et al. Recent Developments and Results on Double Beta Decays with Crystal Scintillators and HPGe Spectrometry. *Universe*. 2018; 4(12):147.
https://doi.org/10.3390/universe4120147

**Chicago/Turabian Style**

Di Marco, Alessandro, Alexander S. Barabash, Pierluigi Belli, Rita Bernabei, Roman S. Boiko, Viktor B. Brudanin, Fabio Cappella, Vincenzo Caracciolo, Riccardo Cerulli, Dmitry M. Chernyak,
and et al. 2018. "Recent Developments and Results on Double Beta Decays with Crystal Scintillators and HPGe Spectrometry" *Universe* 4, no. 12: 147.
https://doi.org/10.3390/universe4120147