Result of the search for neutrinoless double-$\beta$ decay in $^{100}$Mo with the NEMO-3 experiment

R. Arnold (1) , C. Augier (2) , J. d. Baker , A. s. Barabash , A. Basharina-Freshville , S. Blondel (2) , S. Blot , M. Bongrand (2) , V. Brudanin , J. Busto (3) , A. j. Caffrey , S. Calvez (2) , C. Cerna (4) , J. p. Cesar , A. Chapon (5) , E. Chauveau , D. Duchesneau (6) , D. Dominique Durand (5) , V. Egorov , G. Eurin (2) , J. j. Evans , L. Fajt , D. Filosofov , R. Flack , X. Garrido , H. Gómez (2) , B. Guillon (5) , P. Guzowski , R. Hodák , A. Huber (4) , P. Hubert (4) , C. Hugon (4) , Sophie Jullian (2) , A. Klimenko , O. Kochetov , S. i. Konovalov , V. Kovalenko , D. Lalanne (2) , K. Lang , Y. Lemière (5) , T. Le Noblet (6) , Z. Liptak , P. Loaiza (2) , G. Lutter (4) , F. Mamedov , C. Marquet (4) , F. Mauger (5) , B. Morgan , J. Mott , I. Nemchenok , M. Nomachi , F. Nova , F. Nowacki (1) , H. Ohsumi , R. b. Pahlka , F. Perrot (4) , F. Piquemal (7, 4) , P. Povinec , P. Přidal , Y. a. Ramachers , A. Remoto (6) , J. l. Reyss (8, 9) , B. Richards , C. l. Riddle , E. Rukhadze , R. Saakyan , X. Sarazin (2) , Yu. Shitov , L. Simard (10, 2) , F. Šimkovic , A. Smetana , K. Smolek , A. Smolnikov , S. Söldner-Rembold , B. Soulé (4) , I. Štekl , J. Suhonen , C. s. Sutton , G. Szklarz (2) , J. Thomas , V. Timkin , S. Torre , Vl. i. Tretyak , V. i. Tretyak , V. i. Umatov , I. Vanushin , C. Vilela , V. Vorobel , D. Waters , A. Žukauskas

1 IPHC - Institut Pluridisciplinaire Hubert Curien
2 LAL - Laboratoire de l'Accélérateur Linéaire
3 CPPM - Centre de Physique des Particules de Marseille
4 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
5 LPCC - Laboratoire de physique corpusculaire de Caen
6 LAPP - Laboratoire d'Annecy de Physique des Particules
7 LSM - UMR 6417 - Laboratoire Souterrain de Modane
8 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
9 OCEANIS - Océan et Interfaces
10 IUF - Institut universitaire de France

The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double $\beta$ ($0\nu\beta\beta$) decay. We report final results of a search for $0\nu\beta\beta$ decays with $6.914$ kg of $^{100}$Mo using the entire NEMO-3 data set with a detector live time of $4.96$ yr, which corresponds to an exposure of 34.3 kg$\cdot$yr. We perform a detailed study of the expected background in the $0\nu\beta\beta$ signal region and find no evidence of $0\nu\beta\beta$ decays in the data. The level of observed background in the $0\nu\beta\beta$ signal region $[2.8-3.2]$ MeV is $0.44 \pm 0.13$ counts/yr/kg, and no events are observed in the interval $[3.2-10]$ MeV. We therefore derive a lower limit on the half-life of $0\nu\beta\beta$ decays in $^{100}$Mo of $T_{1/2}(0\nu\beta\beta)> 1.1 \times 10^{24}$ yr at the $90\%$ Confidence Level, under the hypothesis of light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range $\langle m_{\nu} \rangle < 0.33$--$0.62$ eV. We also report constraints on other lepton-number violating mechanisms for $0\nu\beta\beta$ decays.

Domaines: Physique des Hautes Energies - Expérience [hep-ex]; Physique Nucléaire Expérimentale [nucl-ex]

R. Arnold, C. Augier, J. d. Baker, A. s. Barabash, A. Basharina-Freshville, et al.. Result of the search for neutrinoless double-$\beta$ decay in $^{100}$Mo with the NEMO-3 experiment. Physical Review D, 2015, 92 (7), ⟨10.1103/PhysRevD.92.072011⟩. ⟨in2p3-01166055⟩