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

TL;DR

This study reports new limits on double beta decay in platinum isotopes and dark matter interactions, using a long-term low-background germanium detector experiment at Gran Sasso, with implications for future research.

Contribution

It provides the most sensitive limits to date on double beta decay modes and dark matter interactions involving platinum isotopes, extending previous bounds and proposing new experimental approaches.

Findings

Limits on double beta decay range from 10^14 to 10^19 years.

Achieved sensitivity greater than 10^19 years for $^{198}$Pt decay modes.

New constraints on inelastic dark matter scattering up to 500 keV mass splitting.

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 $\mathcal{O}(10^{14} - 10^{19})$ yr (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 $10^{19}$ yr, 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.