Ultra-low $Q_{\beta }$ value for the allowed decay of ${}^{110}$Ag${}^m$ confirmed via mass measurements

Abstract

The mass of the electron-antineutrino can be determined in dedicated measurements of the $\beta$ spectral shape near the $\beta$ endpoint of a ${\beta }^{-}$ transition, with a low $Q$ value enhancing the sensitivity of the measurement. One such low-$Q$-value candidate is the transition between the $6^{+}$ isomer of ${}^{110}$Ag and the $5_2^{+}$ state in ${}^{110}$Cd ($Q_{\beta ,m}^{\ast }=-0.12(131)$ keV). To reduce the uncertainty of the $Q$ value, we have used the phase-imaging ion-cyclotron-resonance technique with the JYFLTRAP double Penning trap and performed a high-precision atomic-mass measurement of ${}^{109}$Ag with ${}^{110}$Cd as a reference. Combined with the known spectroscopic data, we obtain a re-evaluated value $Q_{\beta ,m}^{\ast }=405(135)$ eV, for the ${}^{110}\text{Ag}(6_{\text{m}}^{+})\to {}^{110}\text{Cd}(5_2^{+})$ transition. This represents the lowest $Q_{\beta }$ value for any allowed transition observed to date. In order to estimate the partial half-life ($t_{1/2}$) and branching ratio (Br) of the transition, nuclear shell-model calculations were performed using the $jj45pnb$ Hamiltonian in combination with state-of-the-art atomic calculations. The computed values $t_{1/2}=2.23_{-1.28}^{+5.24}\times 10^7$ years and $\text{Br}=3.07_{-2.15}^{+4.16}\times 10^{-8}$, along with the thermal-neutron capture on stable ${}^{109}$Ag as a viable production method, make ${}^{110}{\text{Ag}}^m$ a promising candidate for future antineutrino-mass measurements.

9 pages, 3 figures, 1 additional figure and 3 tables in Supplemental material

References in corpus (14)

• The Design, Construction, and Commissioning of the KATRIN Experiment
• ${}^{159}$Dy electron-capture: a strong new candidate for neutrino mass determination
• $\text{Direct}Q\text{-Value Determination of the}{\beta }^{-}\text{Decay of}{}^{187}\text{Re}$
• Direct measurement of the mass difference of ${}^{72}$As-${}^{72}$Ge rules out ${}^{72}$As as a promising $\beta$-decay candidate to determine the neutrino mass
• Updated evaluation of potential ultra-low Q value $\beta$-decay candidates
• Observation of an ultra-low $Q$-value electron-capture channel decaying to ${}^{75}$As via high-precision mass measurement
• Direct decay-energy measurement as a route to the neutrino mass
• Exchange correction for allowed $\beta$-decay
• High-precision electron-capture $Q$ value measurement of ${}^{111}$In for electron-neutrino mass determination
• Direct determination of the atomic mass difference of the pairs ${}^{76}$As-${}^{76}$Se and ${}^{155}$Tb-${}^{155}$Gd rules out ${}^{76}$As and ${}^{155}$Tb as possible candidates for electron (anti)neutrino mass measurements
• Precise Q value measurements of ${}^{112,113}$Ag and ${}^{115}$Cd with the Canadian Penning trap for evaluation of potential ultra-low Q value $\beta$-decays
• ${\beta }^{-}$ decay $Q$-value measurement of ${}^{136}$Cs and its implications to neutrino studies
• Identification of a potential ultra-low Q value electron capture decay branch in ${}^{75}$Se via a precise Penning trap measurement of the mass of ${}^{75}$As
• High-precision measurements of the atomic mass and electron-capture decay $Q$ value of ${}^{95}$Tc