First limits on double beta decays in ${}^{232}$Th

Abstract

As one of the primordial radioactive isotopes, ${}^{232}$Th mainly undergoes $\alpha$-decay with a half-life of $1.402\times 10^{10}$ yr. However, it is also one of 35 double beta decay candidates in which the single $\beta$-decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle was measured in an HPGe well-detector at the Gran Sasso Underground Laboratory (LNGS) with a total exposure of 3.25 g $\times$ d. We obtain half-life limits on all double beta decay modes of ${}^{232}$Th to excited states of ${}^{232}$U on the order of $10^{11-15}$ yr. For the most likely transition into the $0_1^{+}$ state we find a lower half-life limit of $6.3\times 10^{14}$ yr (90% credibility). These are the first constraints on double beta decay excited state transition in ${}^{232}$Th.

References in corpus (19)

• Search for Majorana Neutrinos near the Inverted Mass Hierarchy Region with KamLAND-Zen
• $0\nu \beta \beta$ and $2\nu \beta \beta$ nuclear matrix elements in the interacting boson model with isospin restoration
• BAT - The Bayesian Analysis Toolkit
• Precise half-life values for two neutrino double beta decay
• Observation of Two-Neutrino Double-Beta Decay in Xe-136 with EXO-200
• Double-beta decay investigation with highly pure enriched ${}^{82}$Se for the LUCIFER experiment
• New results for the two neutrino double beta decay in deformed nuclei with angular momentum projected basis
• First search for double beta decay of platinum by ultra-low background HP Ge gamma spectrometry
• Search of the neutrino-less double beta decay of ${}^{82}$Se into the excited states of ${}^{82}$Kr with CUPID-0
• First search for 2$\epsilon$ and $\epsilon {\beta }^{+}$ processes in ${}^{168}$Yb
• New limits on $2\epsilon$, $\epsilon {\beta }^{+}$ and $2{\beta }^{+}$ decay of ${}^{136}$Ce and ${}^{138}$Ce with deeply purified cerium sample
• Selection rules in the double beta decay of deformed nuclei
• First search for $2\epsilon$ and $\epsilon {\beta }^{+}$ decay of ${}^{162}$Er and new limit on $2{\beta }^{-}$ decay of ${}^{170}$Er to the first excited level of ${}^{170}$Yb
• First search for $2\epsilon$ and $\epsilon {\beta }^{+}$ decay of ${}^{174}$Hf
• First direct search for $2\epsilon$ and $\epsilon {\beta }^{+}$ decay of ${}^{144}$Sm and $2{\beta }^{-}$ decay of ${}^{154}$Sm
• Improved limits on ${\beta }^{+}$EC and ECEC processes in ${}^{74}$Se
• On the possibility to search for double beta decay of initially unstable (alpha/beta radioactive) nuclei
• Double Beta Decays into Excited States in ${}^{110}$Pd and ${}^{102}$Pd
• An improved half-life limit of the double beta decay of ${}^{94}$Zr into the excited state of ${}^{94}$Mo