EDELWEISS-III experiment: Status and first low WIMP mass results

Silvia Scorza

doi:10.1088/1742-6596/718/4/042053

Abstract

The EDELWEISS-III collaboration is operating an experiment for the direct detection of Weakly Interacting Massive Particle (WIMPs) dark matter in the low radioactivity environment of the Modane Underground Laboratory. It consists of 24 advanced high-purity germanium detectors operating at 18 mK in a dilution refrigerator in order to identify rare nuclear recoils induced by elastic scattering of WIMPs from our Galactic halo. The current EDELWEISS-III program, including improvements of the background, data-acquisition and the current installation will be detailed. Sources of background along with the rejection techniques will be discussed. Detector performances and a first low WIMP mass (Boosted Decision Tree) BDT- based analysis of data acquired in a long-term campaign will be presented as well.

Highlights

There is strong observational evidence for the dominance of non-baryonic dark matter over baryonic matter in the universe [1]
It is commonly believed that such a non-baryonic component could consist of new, as yet undiscovered, particles, usually referred to as WIMPs (Weakly Interacting Massive Particles)
The simultaneous measurement of two signals allows an event by event discrimination between electronic recoils caused by photons and beta decays, and nuclear recoils originated from neutrons and WIMPs

Summary

Introduction

There is strong observational evidence for the dominance of non-baryonic dark matter over baryonic matter in the universe [1]. With a dedicated 210Pb calibration, the surface event rejection factor of FID has been measured to be better than 4·10−5 at 90% C.L., with a recoil energy threshold of 15 keV [7], leading to a fiducial volume fraction of 75%. The simultaneous measurement of two signals allows an event by event discrimination between electronic recoils caused by photons and beta decays, and nuclear recoils originated from neutrons and WIMPs. An extensive 133Ba gamma calibration allows us to estimate the FID rejection power of the electronic recoils: no events with an ionization yield lower than 0.5 in a statistics of 4.1×105 gammas, leading to a γ rejection factor better than 6·10−6 at 90% C.L., for a recoil energy threshold of 20 keV [8].

Results

Conclusion