Double-Beta Decay of $^{150}$Nd to Excited Final States

Studying $\beta\beta$ decay with emission of neutrinos (2$\nu\beta\beta$) in particular is important as a check for theoretical models which can be used to calculate the nuclear matrix elements for neutrinoless $\beta\beta$ decay (0$\nu\beta\beta$). These models are needed to obtain the effective electron neutrino mass from 0$\nu\beta\beta$ decay data. In QRPA models, the calculated matrix elements for transitions to the ground state and excited states depend in a different way on the so-called g$_{pp}$ parameter. Therefore, 2$\nu\beta\beta$ decay data to excited states are of special interest. Because SNO+ plans to use $^{150}$Nd as a nuclide in searches for 0$\nu\beta\beta$ decay, our goal is to measure the 2$\nu\beta\beta$ decay of $^{150}$Nd to the first excited 0$^+$ state in $^{150}$Sm. Only tentative information is available for $^{150}$Nd. Here we report our first 6 months of data collection using a 50 g enriched $^{150}$Nd$_2$O$_3$ (43 g $^{150}$Nd) sample placed between two high-purity germanium detectors. We search for the decay of $^{150}$Nd to the first excited 0$^+$ state in $^{150}$Sm by detecting the 334 keV and 406.5 keV deexcitation gamma rays in coincidence. Our apparatus is located at the Kimballton Underground Research Facility (KURF) which provides an overburden of 1450 m.w.e. Singles and coincidence spectra are shown and future plans are discussed. This work was supported by the U.S. Department of Energy, Office of Nuclear Physics under grant number DE--FG02--97ER41033.