Updated and novel limits on double beta decay and dark matter-induced processes in platinum

Abstract

A 510 day long-term measurement of a 45.3 g platinum foil acting as the sample and high voltage contact in an ultra-low-background high purity germanium detector was performed at Laboratori Nazionali del Gran Sasso (Italy). The data was used for a detailed study of double beta decay modes in natural platinum isotopes. Limits are set in the range $O({10}^{14}-{10}^{19})$ years (90% C.L.) for several double beta decay transitions to excited states confirming, and partially extending existing limits. The highest sensitivity of the measurement, greater than ${10}^{19}$ years, was achieved for the two neutrino and neutrinoless double beta decay modes of the isotope ${}^{198}$Pt. Additionally, novel limits for inelastic dark matter scattering on ${}^{195}$Pt are placed up to mass splittings of approximately 500 keV. We analyze several techniques to extend the sensitivity and propose a few approaches for future medium-scale experiments with platinum-group elements.