High-precision measurement of a low Q value for allowed β−-decay of 131I related to neutrino mass determination

• Published in: Physics letters. B Vol. 830; p. 137135
• Main Authors: Eronen, T., Ge, Z., de Roubin, A., Ramalho, M., Kostensalo, J., Kotila, J., Beliushkina, O., Delafosse, C., Geldhof, S., Gins, W., Hukkanen, M., Jokinen, A., Kankainen, A., Moore, I.D., Nesterenko, D.A., Stryjczyk, M., Suhonen, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2022; Elsevier
• Subjects: [formula omitted] decay; Low Q value; Neutrino mass; Penning trap; β− decay; β− decay; Penning trap; Low Q value; Neutrino mass
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2022.137135

The ground-state-to-ground-state β−-decay 131I (7/2+) → 131Xe (3/2+) Q value was determined with high precision utilizing the double Penning trap mass spectrometer JYFLTRAP at the IGISOL facility. The Q value of this β−-decay was found to be Q = 972.25(19) keV through a cyclotron frequency ratio measurement with a relative precision of 1.6 × 10−9. This was realized using the phase-imaging ion-cyclotron-resonance technique. The new Q value is more than 3 times more precise and 2.3σ higher (1.45 keV) than the value extracted from the Atomic Mass Evaluation 2020. Our measurement confirms that the β−-decay to the 9/2+ excited state at 971.22(13) keV in 131Xe is energetically allowed with a Q value of 1.03(23) keV while the decay to the 7/2+ state at 973.11(14) keV was found to be energetically forbidden. Nuclear shell-model calculations with established two-body interactions, alongside an accurate phase-space factor and a statistical analysis of the logft values of known allowed β decays, were used to estimate the partial half-life for the low-Q-value transition to the 9/2+ state. The half-life was found to be (1.97−0.89+2.24) ×107 years, which makes this candidate feasible for neutrino mass searches.