Two-neutrino double-beta decay of ${}^{150}$Nd to excited final states in ${}^{150}$Sm

Abstract

Double-beta decay is a rare nuclear process in which two neutrons in the nucleus are converted to two protons with the emission of two electrons and two electron anti-neutrinos. We measured the half life of the two-neutrino double-beta decay of ${}^{150}$Nd to excited final states of ${}^{150}$Sm by detecting the de-excitation gamma rays of the daughter nucleus. This study yields the first detection of the coincidence gamma rays from the 0${}_1^{+}$ excited state of ${}^{150}$Sm. These gamma rays have energies of 333.97 keV and 406.52 keV, and are emitted in coincidence through a 0${}_1^{+}\to$2${}_1^{+}\to$0${}_{gs}^{+}$ transition. The enriched Nd${}_2$O${}_3$ sample consisted of 40.13 g ${}^{150}$Nd and was observed for 642.8 days at the Kimballton Underground Research Facility, producing 21.6 net events in the region of interest. This count rate gives a half life of $T_{1/2}=(1.07_{-0.25}^{+0.45}(stat)\pm 0.07(syst.))\times 10^{20}$ years. The effective nuclear matrix element was found to be 0.0465${}_{-0.0054}^{+0.0098}$. Finally, lower limits were obtained for decays to higher excited final states. Our half-life measurement agrees within uncertainties with another recent measurement in which no coincidence was employed. Our nuclear matrix element calculation may have an impact on a recent neutrinoless double-beta decay nuclear matrix element calculation which implies the decay to the first excited state in ${}^{150}$Sm is favored over that to the ground state.

16 pages, 15 figures

References in corpus (7)

• Phase space factors for double-$\beta$ decay
• Nuclear matrix elements for double-β decay
• Precise half-life values for two neutrino double beta decay
• Relativistic description of nuclear matrix elements in neutrinoless double-$\beta$ decay
• New Results for Double-Beta Decay of Mo-100 to Excited Final States of Ru-100 Using the TUNL-ITEP Apparatus
• Systematic Law for Half-lives of Double $\beta$-decay with Two Neutrinos
• Low-Background gamma counting at the Kimballton Underground Research Facility

Cited by in corpus (4)

• Average and recommended half-life values for two neutrino double beta decay
• Many-body correlations of quasiparticle random-phase approximation in nuclear matrix element of neutrinoless double-beta decay
• Search for neutrinoless quadruple-$\beta$ decay of ${}^{150}$Nd with the NEMO-3 detector
• Double Beta Decay to the Excited States: Review