A Search for Charged Excitation of Dark Matter with the KamLAND-Zen Detector

TL;DR

This paper reports new constraints on the formation of bound states between dark matter particles and xenon nuclei, using KamLAND-Zen data to set upper limits on interaction cross sections and decay widths for charged excited states of dark matter.

Contribution

It provides the most stringent upper limits to date on the recombination cross section and decay width of charged dark matter excitations using xenon-based liquid scintillator detectors.

Findings

Set upper limits on recombination cross section of 2.0 x 10^{-31} cm^3/s.

Established decay-width constraints of 1.1 x 10^{-18} GeV.

Utilized all xenon isotopes in KamLAND-Zen data for comprehensive analysis.

Abstract

There are many theories where a dark matter particle is part of a multiplet with an electrically charged state. If WIMP dark matter ($\chi^{0}$) is accompanied by a charged excited state ($\chi^{-}$) separated by a small mass difference, it can form a stable bound state with a nucleus. In supersymmetric models, the $\chi^{0}$ and the $\chi^{-}$ could be the neutralino and a charged slepton, such as the neutralino-stau degenerate model. The formation binding process is expected to result in an energy deposition of {\it O}(1--10 MeV), making it suitable for detection in large liquid scintillator detectors. We describe new constraints on the bound state formation with a xenon nucleus using the KamLAND-Zen 400 Phase-II dataset. In order to enlarge the searchable parameter space, all xenon isotopes in the detector were used. For a benchmark parameter set of $m_{\chi^{0}} = 100$ GeV and $\Delta m = 10$ MeV, this study sets the most stringent upper limits on the recombination cross section $\langle\sigma v\rangle$ and the decay-width of $\chi^{-}$ of $2.0 \times 10^{-31}$ ${\rm cm^3/s}$ and $1.1 \times 10^{-18}$ GeV, respectively (90\% confidence level).