Direct high-precision measurement of the mass difference of 77As–77Se related to neutrino mass determination

• Published in: The European physical journal. A, Hadrons and nuclei Hadrons and nuclei, 2024-05, Vol.60 (5)
• Main Authors: Ge, Z., Eronen, T., Ramalho, M., de Roubin, A., Nesterenko, D. A., Kankainen, A., Beliuskina, O., de Groote, R., Geldhof, S., Gins, W., Hukkanen, M., Jokinen, A., Koszorús, Á., Kotila, J., Kostensalo, J., Moore, I. D., Pirinen, P., Raggio, A., Rinta-Antila, S., Sevestrean, V. A., Suhonen, J., Virtanen, V., Zadvornaya, A.
• Format: Article
• Language: English
• Subjects: Hadrons; Heavy Ions; Nuclear Fusion; Nuclear Physics; Particle and Nuclear Physics; Physics; Physics and Astronomy; Regular Article - Experimental Physics
• ISSN: 1434-601X
• DOI: 10.1140/epja/s10050-024-01317-3

The first direct determination of the ground-state-to-ground-state β - -decay Q -value of 77 As to 77 Se was performed by measuring their atomic mass difference utilizing the double Penning trap mass spectrometer, JYFLTRAP. The resulting Q -value is 684.463(70) keV, representing a remarkable 24-fold improvement in precision compared to the value reported in the most recent Atomic Mass Evaluation (AME2020). With the significant reduction of the uncertainty of the ground-state-to-ground-state Q -value and knowledge of the excitation energies in 77 Se from γ -ray spectroscopy, the ground-state-to-excited-state Q -value of the transition 77 As (3/2 - , ground state) → 77 Se ∗ (5/2 + , 680.1035(17) keV) was refined to be 4.360(70) keV. We confirm that this potential low Q -value β - -decay transition for neutrino mass determination is energetically allowed at a confidence level of about 60 σ . Nuclear shell-model calculations with two well-established effective Hamiltonians were used to estimate the partial half-life for the low Q -value transition. The half-life was found to be of the order of 10 9 years for this first-forbidden non-unique transition. Since the half-life of 77 As is only ≈ 2 days, usage of it as source for rare-event experiments searching for the electron antineutrino mass would be challenging.