New limits on double-beta decay of $^{190}$Pt and $^{198}$Pt

TL;DR

This study conducted a sensitive search for double-beta decay in platinum isotopes, setting new lower bounds on their half-lives and exploring potential resonant decay modes with advanced underground detection techniques.

Contribution

The paper presents the first limits on resonant $0 u KN$ decay of $^{190}$Pt and significantly improves the half-life limits for $^{198}$Pt decay modes.

Findings

Lower limits on half-lives of $^{190}$Pt decay: $10^{14}-10^{16}$ years.

First limit on resonant $0 u KN$ transition: $ ext{T}_{1/2} ext{ ≥ } 2.5 imes 10^{16}$ years.

Enhanced lower limit on $^{198}$Pt decay: $ ext{T}_{1/2} ext{ ≥ } 3.2 imes 10^{19}$ years.

Abstract

A search for double-beta decay of $^{190}$Pt and $^{198}$Pt with emission of $\gamma$-ray quanta was realized at the HADES underground laboratory with a 148 g platinum sample measured by two ultralow-background HPGe detectors over 8946 h. The isotopic composition of the platinum sample has been measured with high precision using inductively coupled plasma mass spectrometry. New lower limits for the half-lives of $^{190}$Pt relative to different channels and modes of the decays were set on the level of $\lim T_{1/2}\sim 10^{14}-10^{16}$ yr. A possible exact resonant $0\nu KN$ transition to the 1,2 1326.9 keV level of $^{190}$Os is limited for the first time as $T_{1/2} \geq 2.5 \times10^{16}$ yr. A new lower limit on the double-beta decay of $^{198}$Pt to the first excited level of $^{198}$Hg was set as $T_{1/2} \geq 3.2\times10^{19}$ yr, one order of magnitude higher than the limit obtained in the previous experiment.