# Search for WIMP Inelastic Scattering off Xenon Nuclei with XENON100

## TL;DR

This paper reports the first constraints on inelastic spin-dependent WIMP scattering off xenon nuclei using XENON100 data, setting the most stringent upper limits to date and guiding future larger detector analyses.

## Contribution

It provides the first experimental limits on inelastic WIMP-nucleon interactions in xenon, expanding the search for dark matter beyond elastic scattering channels.

## Key findings

- No evidence for inelastic WIMP-$^{129}$Xe interactions was observed.
- Set a 90% C.L. upper limit of $3.3 imes 10^{-38}$ cm$^{2}$ at 100 GeV/c$^2$.
- Results are the most constraining to date for this interaction channel.

## Abstract

We present the first constraints on the spin-dependent, inelastic scattering cross section of Weakly Interacting Massive Particles (WIMPs) on nucleons from XENON100 data with an exposure of 7.64$\times$10$^3$\,kg\,day. XENON100 is a dual-phase xenon time projection chamber with 62\,kg of active mass, operated at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy and designed to search for nuclear recoils from WIMP-nucleus interactions. Here we explore inelastic scattering, where a transition to a low-lying excited nuclear state of $^{129}$Xe is induced. The experimental signature is a nuclear recoil observed together with the prompt de-excitation photon. We see no evidence for such inelastic WIMP-$^{129}$Xe interactions. A profile likelihood analysis allows us to set a 90\% C.L. upper limit on the inelastic, spin-dependent WIMP-nucleon cross section of $3.3 \times 10^{-38}$\,cm$^{2}$ at 100\,GeV/c$^2$. This is the most constraining result to date, and sets the pathway for an analysis of this interaction channel in upcoming, larger dual-phase xenon detectors.