Recent advancements of the experiment to search for $2K$-capture in $^{124}$Xe using a Large Low-background Proportional Counter

TL;DR

This paper introduces a new correction method for charge signals in large proportional counters, enhancing the detection sensitivity for $2 u2K$-decay in $^{124}$Xe over long-term experiments.

Contribution

It presents a novel correction technique for charge signals that improves event selection efficiency and sensitivity in $2 u2K$-decay searches with large proportional counters.

Findings

Increased detection sensitivity to $2 u2K$-decay in $^{124}$Xe.

Successful registration of double $K$ photoionization events.

Enhanced data analysis accuracy with the new correction method.

Abstract

A new method for correcting the charge signal from the large proportional counter is proposed. The correction method makes it possible to take into account the loss of primary ionization electrons in the presence of weakly increasing micro impurities of electronegative gases during long-term measurements. It allows increasing the efficiency of the selection of useful events and thereby increasing the sensitivity to $2\nu2K$-decay in $^{124}$Xe at the level of $2\times10^{22}$ from over six years of measurements using a large proportional counter. Analysis of the calibration data, taking into account the new method for correcting the energy release in the detector, made it possible to register events from double $K$ photoionization by a single photon.