Optimizing EDELWEISS detectors for low-mass WIMP searches

TL;DR

This paper evaluates and optimizes EDELWEISS detectors for detecting low-mass WIMPs, projecting sensitivity improvements and background reduction strategies for future experiments, including neutrino background considerations.

Contribution

It introduces a data-driven background model and analysis strategies tailored for low-mass WIMP detection, optimizing detector performance for different mass ranges.

Findings

Projected WIMP-nucleon cross-section limit of 7×10⁻⁴² cm² for 2-5 GeV/c² WIMPs by 2018.

Optimal detection strategies vary depending on WIMP mass, especially below or above 5 GeV/c².

Future experiments could detect solar neutrino events with improved ionization resolution and lower backgrounds.

Abstract

The physics potential of EDELWEISS detectors for the search of low-mass Weakly Interacting Massive Particles (WIMPs) is studied. Using a data-driven background model, projected exclusion limits are computed using frequentist and multivariate analysis approaches, namely profile likelihood and boosted decision tree. Both current and achievable experimental performance are considered. The optimal strategy for detector optimization depends critically on whether the emphasis is put on WIMP masses below or above $\sim$ 5 GeV/c$^2$. The projected sensitivity for the next phase of the EDELWEISS-III experiment at the Modane Underground Laboratory (LSM) for low-mass WIMP search is presented. By 2018 an upper limit on the spin-independent WIMP-nucleon cross-section of $\sigma_{SI} = 7 \times 10^{-42}$ cm$^2$ is expected for a WIMP mass in the range 2$-$5 GeV/c$^2$. The requirements for a future hundred-kilogram scale experiment designed to reach the bounds imposed by the coherent scattering of solar neutrinos are also described. By improving the ionization resolution down to 50 eV$_{ee}$, we show that such an experiment installed in an even lower background environment (e.g. at SNOLAB) should allow to observe about 80 $^8$B neutrino events after discrimination.