2K(2\nu)-Capture in Xe-124: Results of Data Processing for an Exposure of 37.7 kg x day

TL;DR

This paper reports on the search for two-neutrino double K-capture in xenon-124 using a copper proportional counter, setting a new lower limit on its half-life after analyzing 37.7 kg·day of data at a deep underground laboratory.

Contribution

It introduces a novel data processing method and background suppression technique for detecting rare double K-capture events in xenon-124.

Findings

New half-life lower limit: T₁/₂ ≥ 7.7×10²¹ years at 90% C.L.

Effective background suppression in the energy region of interest.

Successful application of data processing methods in a low-background underground setup.

Abstract

The results of the experimental search for two-neutrino $2K$-capture in $^{124}$Xe with a large copper proportional counter obtained by processing the data for an exposure of 37.7 kg$\times$day are presented. The experimental setup is located at the Underground Low-Background Laboratory of the Baksan Neutrino Observatory at a depth of 4900 m w.e. The combination of methods of selection of useful signals with a unique set of characteristics and the event topology taken into account allowed us to suppress the background in the energy region of interest. A new half-life limit for $2K(2\nu)$-capture in $^{124}$Xe was determined: T$_{1/2}\geq7.7\cdot10^{21}$ yrs (90\% C.L.).