Search for WIMP-$^{129}$Xe inelastic scattering with particle identification in XMASS-I

TL;DR

This study used the XMASS-I detector to search for inelastic scattering of WIMPs on xenon nuclei, setting new stringent limits on the interaction cross section, especially for SD WIMP-neutron interactions, without detecting a signal.

Contribution

The paper presents the most sensitive limits to date on inelastic WIMP-xenon interactions, utilizing improved background evaluation and event classification techniques.

Findings

No WIMP signal was observed.

Set the most stringent limits on SD WIMP-neutron cross section.

Improved sensitivity by a factor of 7.7 at 200 GeV/c^2.

Abstract

A search for Weakly Interacting Massive Particles (WIMPs) was conducted with the single-phase liquid-xenon detector XMASS through inelastic scattering in which $^{129}$Xe nuclei were excited, using an exposure ($\rm 327\; kg \times 800.0 \; days$) 48 times larger than that of our previous study. The inelastic excitation sensitivity was improved by detailed evaluation of background, event classification based on scintillation timing that distinguished $\gamma$-rays and $\beta$-rays, and simultaneous fitting of the energy spectra of $\gamma$-like and $\beta$-like samples. No evidence of a WIMP signal was found. Thus, we set the upper limits of the inelastic channel cross section at 90\% confidence level, for example, $4.1\times 10^{-39} \;{\rm cm^2}$ for a $200\; {\rm GeV}/c^2$ WIMP. This result provides the most stringent limits on the SD WIMP-neutron interaction and is better by a factor of 7.7 at $200\;{\rm GeV}/c^2$ than the existing experimental limit.