Sensitivity of the NEXT experiment to Xe-124 double electron capture

J Díaz, D González-Díaz, M Kekic, L Labarga, A Laing, P Lebrun, N López-March, M Losada, R. D. P Mano, J Martín-Albo, A Martínez, A. D McDonald, F Monrabal, C. M. B Monteiro, F. J Mora, J. Muñoz Vidal, P Novella, D. R Nygren, B Palmeiro, A ParaJ Pérez, M Querol, J Renner, J Repond, S Riordan, L Ripoll, Y. Rodríguez García, J Rodríguez, L Rogers, B Romeo, C Romo-Luque, F. P Santos, J. M. F. dos Santos, C Sofka, T Stiegler, J. F Toledo, J Torrent, A Usón, J. F. C. A Veloso, R Webb, J. T White, K Woodruff, N Yahlali,

Research output: Contribution to journalArticlepeer-review

Abstract

Double electron capture by proton-rich nuclei is a second-order nuclearprocess analogous to double beta decay. Despite their similarities, the decaysignature is quite different, potentially providing a new channel to measurethe hypothesized neutrinoless mode of these decays. The Standard-Model-allowedtwo-neutrino double electron capture ($2\nu ECEC$) has been predicted for anumber of isotopes, but only observed in $^{78}$Kr, $^{130}$Ba and, recently,$^{124}$Xe. The sensitivity to this decay establishes a benchmark for theultimate experimental goal, namely the potential to discover also thelepton-number-violating neutrinoless version of this process, $0\nu ECEC$. Herewe report on the current sensitivity of the NEXT-White detector to $^{124}$Xe$2\nu ECEC$ and on the extrapolation to NEXT-100. Using simulated data for the$2\nu ECEC$ signal and real data from NEXT-White operated with$^{124}$Xe-depleted gas as background, we define an optimal event selectionthat maximizes the NEXT-White sensitivity. We estimate that, for NEXT-100operated with xenon gas isotopically enriched with 1 kg of $^{124}$Xe and for a5-year run, a sensitivity to the $2\nu ECEC$ half-life of $6 \times 10^{22}$ y(at 90% confidence level) or better can be reached.
Original languageEnglish
Article number203
Number of pages25
JournalThe journal of high energy physics
Volume2021
Issue number2
DOIs
StatePublished - 24 Feb 2021

Keywords

  • Dark Matter and Double Beta Decay (experiments)

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics

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