Search for inelastic WIMP-iodine scattering with COSINE-100

TL;DR

This study searched for inelastic WIMP-iodine interactions using NaI(Tl) detectors in COSINE-100, finding no evidence and setting upper limits on the interaction cross section at high WIMP masses.

Contribution

First search for inelastic WIMP-iodine scattering with NaI(Tl) detectors, establishing new upper limits on the cross section at 500 GeV/c² WIMP mass.

Findings

No evidence of inelastic WIMP-iodine scattering detected.

Set 90% CL upper limit on cross section: 1.2 x 10^{-37} cm² at 500 GeV/c².

Demonstrated the sensitivity of COSINE-100 to inelastic WIMP interactions.

Abstract

We report the results of a search for inelastic scattering of weakly interacting massive particles (WIMPs) off $^{127}$I nuclei using NaI(Tl) crystals with a data exposure of 97.7 kg$\cdot$years from the COSINE-100 experiment. The signature of inelastic WIMP-$^{127}$I scattering is a nuclear recoil accompanied by a 57.6 keV $\gamma$-ray from the prompt deexcitation, producing a more energetic signal compared to the typical WIMP nuclear recoil signal. We found no evidence for this inelastic scattering signature and set a 90 $\%$ confidence level upper limit on the WIMP-proton spin-dependent, inelastic scattering cross section of $1.2 \times 10^{-37} {\rm cm^{2}}$ at the WIMP mass 500 ${\rm GeV/c^{2}}$.