Sensitivity of the NEXT experiment to Xe-124 double electron capture
Creators: name: Martínez-Lema, G.
name: Martínez-Vara, M.
name: Sorel, M.
name: Adams, C.
name: Alvarez, V.
name: Arazi, L.
name: Arnquist, I. J.
name: Azevedo, C. D. R
name: Bailey, K.
name: Ballester, F.
name: Benlloch-Rodríguez, J. M.
name: Borges, F. I. G. M.
name: Byrnes, N.
name: Cárcel, S.
name: Carrión, J. V.
name: Cebrián, S.
name: Church, E.
name: Conde, C. A. N.
name: Contreras, T.
name: Díaz, G.
name: Díaz, J.
name: Diesburg, M.
name: Escada, J.
name: Esteve, R.
name: Felkai, R.
name: Fernandes, A. F. M.
name: Fernandes, L. M. P.
name: Ferrario, P.
name: Ferreira, A. L.
name: Freitas, E. D. C.
name: Generowicz, J.
name: Ghosh, S.
name: Goldschmidt, A.
name: Gómez-Cadenas, J. J.
name: González-Díaz, D.
name: Guenette, R.
name: Gutiérrez, R. M.
name: Haefner, J.
name: Hafidi, K.
name: Hauptman, J.
name: Henriques, C. A. O.
name: Morata, J. A. Hernando
name: Herrero, P.
name: Herrero, V.
name: Ifergan, Y.
name: Johnston, S.
name: Jones, B. J. P.
name: Kekic, M.
name: Labarga, L.
name: Laing, A.
name: Lebrun, P.
name: López-March, N.
name: Losada, M.
name: Mano, R. D. P.
name: Martín-Albo, J.
name: Martínez, A.
name: McDonald, A. D.
name: Monrabal, F.
name: Monteiro, C. M. B.
name: Mora, F. J.
name: Vidal, J. Muñoz
name: Novella, P.
name: Nygren, D. R.
name: Palmeiro, B.
name: Para, A.
name: Pérez, J.
name: Querol, M.
name: Redwine, A. B.
name: Renner, J.
name: Repond, J.
name: Riordan, S.
name: Ripoll, L.
name: García, Y. Rodríguez
name: Rodríguez, J.
name: Rogers, L.
name: Romeo, B.
name: Romo-Luque, C.
name: Santos, F. P.
name: Santos, J. M. F. dos
name: Simón, A.
name: Sofka, C.
name: Stiegler, T.
name: Toledo, J. F.
name: Torrent, J.
name: Usón, A.
name: Veloso, J. F. C. A.
name: Webb, R.
name: Weiss-Babai, R.
name: White, J. T.
name: Woodruff, K.
name: Yahlali, N.
Publisher: name: arXiv
Year: 2020
Subjects: subject: High Energy Physics - Experiment (hep-ex)
subject: Nuclear Experiment (nucl-ex)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Double electron capture by proton-rich nuclei is a second-order nuclear process analogous to double beta decay. Despite their similarities, the decay signature is quite different, potentially providing a new channel to measure the hypothesized neutrinoless mode of these decays. The Standard-Model-allowed two-neutrino double electron capture ($2νECEC$) has been predicted for a number of isotopes, but only observed in $^{78}$Kr, $^{130}$Ba and, recently, $^{124}$Xe. The sensitivity to this decay establishes a benchmark for the ultimate experimental goal, namely the potential to discover also the lepton-number-violating neutrinoless version of this process, $0νECEC$. Here we report on the current sensitivity of the NEXT-White detector to $^{124}$Xe $2νECEC$ and on the extrapolation to NEXT-100. Using simulated data for the $2νECEC$ signal and real data from NEXT-White operated with $^{124}$Xe-depleted gas as background, we define an optimal event selection that maximizes the NEXT-White sensitivity. We estimate that, for NEXT-100 operated with xenon gas isotopically enriched with 1 kg of $^{124}$Xe and for a 5-year run, a sensitivity to the $2νECEC$ half-life of $6 \times 10^{22}$ y (at 90% confidence level) or better can be reached.
description: 23 pages, 13 figures