A low-mass dark matter search using ionization signals in XENON100

TL;DR

This paper reports a low-mass dark matter search using ionization signals in XENON100, achieving a low energy threshold and setting new upper limits on WIMP-nucleon interactions for WIMPs around 6 GeV/c².

Contribution

It introduces a method that uses only ionization signals to lower the detection threshold in dark matter searches, enabling exploration of lower WIMP masses.

Findings

Set an upper limit on WIMP-nucleon cross section at 6 GeV/c²

Lowered energy detection threshold to 0.7 keV

Excluded certain low-mass WIMPs at 90% confidence level

Abstract

We perform a low-mass dark matter search using an exposure of 30\,kg$\times$yr with the XENON100 detector. By dropping the requirement of a scintillation signal and using only the ionization signal to determine the interaction energy, we lowered the energy threshold for detection to 0.7\,keV for nuclear recoils. No dark matter detection can be claimed because a complete background model cannot be constructed without a primary scintillation signal. Instead, we compute an upper limit on the WIMP-nucleon scattering cross section under the assumption that every event passing our selection criteria could be a signal event. Using an energy interval from 0.7\,keV to 9.1\,keV, we derive a limit on the spin-independent WIMP-nucleon cross section that excludes WIMPs with a mass of 6\,GeV/$c^2$ above $1.4 \times 10^{-41}$\,cm$^2$ at 90\% confidence level.