Karlsruhe School of Elementary Particle and Astroparticle Physics: Science and Technology (KSETA)

Cecile Kefelian


Institute: IKP (CN)
Room: 107 bld. 402 (CN)
Phone: +49 721 608 2 4971
Email KIT: cecile.kefelian#partner.kit.edu
Email IPNL : kefelian#ipnl.in2p3.fr
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PhD Thesis (finished on the 5th of February 2016 with magna cum laude)

Co-supervised PhD between the Institute of Nuclear Physics of Lyon (IPNL), France and the Karlsruhe Institute for Technology (KIT), Germany in the EDELWEISS collaboration on the topic:

Search of dark matter with EDELWEISS III excluding background from muon-induced neutrons

Referee: Prof. J. Bluemer
Co-referee: Prof. J. Jochum
Advisor: Dr. K. Eitel


The aim of the EDELWEISS-III experiment is to detect the elastic scattering of WIMPs from the galactic dark matter halo on germanium bolometers. The most problematic background arises from neutrons, which can mimic a WIMP interaction in a detector. Neutrons are notably induced by high energy cosmic ray muons reaching the underground laboratory despite the 1700 m of rock overburden. Remaining muons are tagged using an active muon-veto system of 46 plastic scintillator modules surrounding the experiment, which allows rejecting most of the associated background. The goal of this thesis was to give a precise estimation of the irreducible muon-induced neutron background, needed to identify a potential WIMP signal. The expected background depends on the geometry of the experiment as well as on the used materials, both significantly modified since EDELWEISS-II. GEANT4-based simulations of muons through the modified geometry were performed to derive the rate of events induced by muons in the bolometer array. This rate has been shown to be in good agreement with the measured one extracted from the data. In parallel, a lower limit on the muon-veto efficiency was derived using bolometer data only. A new method based on the use of an AmBe source was developed to extract precisely the detection efficiency of individual modules from the simulation. These results demonstrate that the expected background is negligible for the WIMP search analyses performed with the data of the EDELWEISS-III experiment and will not limit its future sensitivity.


Publications in refereed journals

  • E. Armengaud et al., Axion searches with the EDELWEISS-II experiment, JCAP11(2013)067

  • C. Kéfélian, Status of the EDELWEISS-III Dark Matter search, J. Phys.: Conf. Ser. 606 012002, 2015

  • E. Armengaud et al., Development and underground test of radiopure ZnMoO4 scintillating bolometers for the LUMINEU 0?2ß project LUMINEU and EDELWEISS Collaborations, JINST 10 (2015) P05007

  • Other publications

  • C. Kéfélian, Improvements of the muon veto efficiency towards the EDELWEISS-III experiment, in Proceedings des Journées de Rencontre des Jeunes Chercheurs, Dec 2013, Barbaste, France, https://indico.in2p3.fr/event/8599/contributions 5

  • Seminar and talks at conferences and workshops

    KSETA Topical courses I followed

    • Detector technology in direct Dark Matter searches
    • Elementary particle physics and cosmology for engineers (and others)
    • Introduction to astroparticle physics, cosmology and neutrino physics
    • Parallel programming and graphical processors in scientific applications
    • Accelarator based particle physics for astroparticle physicists
    • The long journey to the Higgs boson and beyond at the LHC
    • Collaborative tools for software development
    • Data analysis and statistics for theoretician
    • Supersymmetry in particle physics and cosmology
    • Data visualization and presenting
    • Memorizing, reading and working strategies
    • What do I need, if I will leave science towards industry?


      Winter semester 2013/2014 Advanced lab work of Nuclear Physics of the Physics Faculty Supervisor of the two lab works "Gamma spectroscopie” and “Landé effect”

    KSETA Reports