Measurement of the $2\nu\beta\beta$ decay rate and spectral shape of $^{100}$Mo from the CUPID-Mo experiment

Author:

C. Augier, A. S. Barabash, F. Bellini, G. Benato, 6 M. Beretta, L. Berge, J. Billard, Yu. A. Borovlev, L. Cardani, N. Casali, A. Cazes, E. Celi, M. Chapellier, D. Chiesa, I. Dafinei, F. A. Danevich, M. De Jesus, T. Dixon, L. Dumoulin, K. Eitel, F. Ferri, B. K. Fujikawa, J. Gascon, L. Gironi, A. Giuliani, V. D. Grigorieva, M. Gros, D. L. Helis, H. Z. Huang, R. Huang, L. Imbert, J. Johnston, A. Juillard, H. Khalife, M. Kleifges, V. V. Kobychev, Yu. G. Kolomensky, S. I. Konovalov, J. Kotila, P. Loaiza, L. Ma, E. P. Makarov, P. de Marcillac, R. Mariam, L. Marini, S. Marnieros, X. -F. Navick, C. Nones, E. B. Norman, E. Olivieri, J. L. Ouellet, L. Pagnanini, L. Pattavina, B. Paul, M. Pavan, H. Peng, G. Pessina, S. Pirro, D. V. Poda, O. G. Polischuk, S. Pozzi, E. Previtali, Th. Redon, A. Rojas, S. Rozov, V. Sanglard, J. A. Scarpaci, B. Schmidt, Y. Shen, V. N. Shlegel, F. Simkovic, V. Singh, C. Tomei, V. I. Tretyak, V. I. Umatov, L. Vagneron, M. Velazquez, B. Ware, B. Welliver, L. Winslow, M. Xue, E. Yakushev, M. Zarytskyy, A. S. Zolotarova

Keyword:

Nuclear Experiment, Nuclear Experiment (nucl-ex), High Energy Physics - Experiment (hep-ex)

journal:

date:

2023-07-25 16:00:00

Abstract

Neutrinoless double beta decay ($0\nu\beta\beta$) is a yet unobserved nuclear process which would demonstrate Lepton Number violation, a clear evidence of beyond Standard Model physics. The process two neutrino double beta decay ($2\nu\beta\beta)$ is allowed by the Standard Model and has been measured in numerous experiments. In this letter, we report a measurement of $2\nu\beta\beta$ decay half-life of $^{100}$Mo to the ground state of $^{100}$Ru of $(7.07~\pm~0.02~\text{(stat.)}~\pm~0.11~\text{(syst.)})~\times~10^{18}$~yr by the CUPID-Mo experiment. With a relative precision of $\pm~1.6$ \% this is the most precise measurement to date of a $2\nu\beta\beta$ decay rate in $^{100}$Mo. In addition, we constrain higher-order corrections to the spectral shape which provides complementary nuclear structure information. We report a novel measurement of the shape factor $\xi_{3,1}=0.45~\pm 0.03~\text{(stat.)} \ \pm 0.05 \ \text{(syst.)}$, which is compared to theoretical predictions for different nuclear models. We also extract the first value for the effective axial vector coupling constant obtained from a spectral shape study of $2\nu\beta\beta$ decay.

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