https://doi.org/10.1140/epjc/s10052-016-4388-y
Regular Article - Experimental Physics
Improved EDELWEISS-III sensitivity for low-mass WIMPs using a profile likelihood approach
1
Karlsruher Institut für Technologie, Institut für Kernphysik, Postfach 3640, 76021, Karlsruhe, Germany
2
CEA Saclay, DSM/IRFU, 91191, Gif-sur-Yvette Cedex, France
3
Univ Lyon, Université Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique nucléaire de Lyon, 4 rue Enrico Fermi, F-69622, Lyon, France
4
Institut Néel, CNRS/UJF, 25 rue des Martyrs, BP 166, 38042, Grenoble, France
5
CSNSM, Univ. Paris-Sud, CNRS/IN2P3, Université Paris-Saclay, 91405, Orsay, France
6
Karlsruher Institut für Technologie, Institut für Experimentelle Kernphysik, Gaedestr. 1, 76128, Karlsruhe, Germany
7
Laboratoire de Photonique et de Nanostructures, CNRS, Route de Nozay, 91460, Marcoussis, France
8
Karlsruher Institut für Technologie, Institut für Prozessdatenverarbeitung und Elektronik, Postfach 3640, 76021, Karlsruhe, Germany
9
Department of Physics, University of Oxford, Keble Road, Oxford, OX1 3RH, UK
10
Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield, S3 7RH, UK
11
CEA Saclay, DSM/IRAMIS, 91191, Gif-sur-Yvette Cedex, France
12
JINR, Laboratory of Nuclear Problems, Joliot-Curie 6, 141980, Dubna, Moscow Region, Russian Federation
13
Queen’s University, Kingston, Canada
14
Rensselaer Polytechnic Institute, Troy, NY, USA
15
Lawrence Berkeley National Laboratory, Berkeley, CA, USA
* e-mail: lukas.hehn@kit.edu
Received:
13
July
2016
Accepted:
19
September
2016
Published online:
6
October
2016
We report on a dark matter search for a Weakly Interacting Massive Particle (WIMP) in the mass range with the EDELWEISS-III experiment. A 2D profile likelihood analysis is performed on data from eight selected detectors with the lowest energy thresholds leading to a combined fiducial exposure of 496 kg-days. External backgrounds from
- and
-radiation, recoils from
and neutrons as well as detector intrinsic backgrounds were modelled from data outside the region of interest and constrained in the analysis. The basic data selection and most of the background models are the same as those used in a previously published analysis based on boosted decision trees (BDT) [1]. For the likelihood approach applied in the analysis presented here, a larger signal efficiency and a subtraction of the expected background lead to a higher sensitivity, especially for the lowest WIMP masses probed. No statistically significant signal was found and upper limits on the spin-independent WIMP-nucleon scattering cross section can be set with a hypothesis test based on the profile likelihood test statistics. The 90 % C.L. exclusion limit set for WIMPs with
is
, which is an improvement of a factor of seven with respect to the BDT-based analysis. For WIMP masses above
the exclusion limits found with both analyses are in good agreement.
© The Author(s), 2016