Double Beta Decays into Excited States in $^{110}$Pd and $^{102}$Pd

TL;DR

This study searches for double beta decays into excited states of palladium isotopes using gamma-spectrometry, setting new half-life limits and improving detection sensitivity across multiple laboratories.

Contribution

It provides the first combined Bayesian analysis of three gamma-spectrometry measurements to set improved half-life limits for double beta decay modes in $^{110}$Pd and $^{102}$Pd.

Findings

Set new half-life limits for $^{110}$Pd and $^{102}$Pd decay modes.

Combined data from three laboratories enhances sensitivity.

No positive detection of double beta decay observed.

Abstract

A search for double beta decays of $^{110}$Pd and $^{102}$Pd into excited states of the daughter nuclides has been performed using three ultra-low background gamma-spectrometry measurements in the Felsenkeller laboratory, Germany, the HADES laboratory, Belgium and at the LNGS, Italy. The combined Bayesian analysis of the three measurements sets improved half-life limits for the $2\nu\beta\beta$ and $0\nu\beta\beta$ decay modes of the $2^+_1$, $0^+_1$ and $2^+_2$ transitions in $^{110}$Pd to $2.9\cdot10^{20}$ yr, $4.0\cdot10^{20}$ yr and $3.0\cdot10^{20}$ yr respectively and in $^{102}$Pd to $7.6\cdot10^{18}$ yr, $8.8\cdot10^{18}$ yr and $1.4\cdot10^{19}$ yr respectively with 90% credibility.