Search for neutrinoless <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mi>β</mml:mi><mml:mo>+</mml:mo></mml:msup></mml:math>EC decay of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Te</mml:mi><mml:mprescripts/><mml:none/><mml:mn>120</mml:mn></mml:mmultiscripts></mml:math> with CUORE
Douglas Q. Adams, C. Alduino, K. Alfonso, F. T. Avignone, O. Azzolini, G. Bari, F. Bellini, G. Benato, M. Beretta, M. Biassoni, A. Branca, C. Brofferio, C. Bucci, J. Camilleri, A. Caminata, A. Campani, L. Canonica, X. G. Cao, C. Capelli, S. Capelli, L. Cappelli, L. Cardani, P. Carniti, N. Casali, E. Celi, D. Chiesa, M. Clemenza, S. Copello, O. Cremonesi, R. J. Creswick, A. D’Addabbo, I. Dafinei, F. Del Corso, S. Dell’Oro, S. Di Domizio, S. Di Lorenzo, V. Dompè, D. Q. Fang, G. Fantini, M. Faverzani, E. Ferri, F. Ferroni, E. Fiorini, A. Franceschi, S. J. Freedman, S. Fu, B. K. Fujikawa, S. Ghislandi, A. Giachero, A. Gianvecchio, L. Gironi, A. Giuliani, P. Gorla, C. Gotti, T. D. Gutierrez, K. Han, E. V. Hansen, K. M. Heeger, R.G. Huang, H. Z. Huang, J. Johnston, G. Keppel, Yu. G. Kolomensky, Robert G. Kowalski, C. Ligi, R. Liu, L. Ma, Y. G., L. Marini, R. Maruyama, D. Mayer, Y. Mei, S. Morganti, T. Napolitano, M. Nastasi, J. A. Nikkel, C. Nones, E. B. Norman, A. Nucciotti, I. Nutini, T. O’Donnell, M. Olmi, J. L. Ouellet, S. Pagan, C. Pagliarone, L. Pagnanini, M. Pallavicini, L. Pattavina, M. Pavan, G. Pessina, V. Pettinacci, C. Pira, S. Pirro, S. Pozzi, E. Previtali, A. Puiu, S. Quitadamo, A. Ressa, C. Rosenfeld, M. Sakai
Abstract
The Cryogenic Underground Observatory for Rare Events (CUORE) is a large-scale cryogenic experiment searching for neutrinoless double-beta decay ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$) in $^{130}\mathrm{Te}$. The CUORE detector is made of natural tellurium, providing the possibility of rare event searches on isotopes other than $^{130}\mathrm{Te}$. In this work we describe a search for neutrinoless positron-emitting electron capture (${\ensuremath{\beta}}^{+}\mathrm{EC}$) decay in $^{120}\mathrm{Te}$ with a total ${\mathrm{TeO}}_{2}$ exposure of 355.7 kg yr, corresponding to 0.2405 kg yr of $^{120}\mathrm{Te}$. Albeit $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ with two final-state electrons represents the most promising channel, the emission of a positron and two 511-keV $\ensuremath{\gamma}$'s make $0\ensuremath{\nu}{\ensuremath{\beta}}^{+}\mathrm{EC}$ decay signature extremely clear. To fully exploit the potential offered by the detector modularity we include events with different topology and perform a simultaneous fit of five selected signal signatures. Using blinded data we extract a median exclusion sensitivity of $3.4\ifmmode\times\else\texttimes\fi{}{10}^{22}$ yr at 90% credibility interval (C.I.). After unblinding we find no evidence of $0\ensuremath{\nu}{\ensuremath{\beta}}^{+}\mathrm{EC}$ signal and set a 90% C.I. Bayesian lower limit of $2.9\ifmmode\times\else\texttimes\fi{}{10}^{22}$ yr on $^{120}\mathrm{Te}$ half-life. This result improves by an order of magnitude the existing limit from the combined analysis of CUORE-0 and Cuoricino.