Cecile Kefelian

Information

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
Linkedin profile

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

Summary

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

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

• Workshop on germanium-based technologies (September 14^th – 17 ^th 2014), Vermillion, South-Dakota (USA)
  Talk: "Status of the EDELWEISS-III Dark Matter search"
  
• Seminar on PhD work at the Institute of Nuclear Physics of Lyon, "Étude du bruit de fond neutrons induits par les muons cosmiques dans l’expérience de recherche de matière noire EDELWEISS-III" (14th of November 2014), Lyon (France)
• Journées des jeunes chercheurs (December 1^th – 7 ^th 2013), Barbaste (France)
  Talk: "The muon veto system of the EDELWEISS dark matter experiment"
  Proceedings: "Improvements of the muon veto efficiency towards the EDELWEISS-III experiment"
• Workshop "New perspectives in dark matter" (October 22^th to 25^th 2013), Lyon (France)
  Poster: "The EDELWEISS muon veto: achievements and improvements"
• KSETA PhD Workshop (October 16^th to 18^th 2013), Freudenstadt
  Tutorial: "Data analysis using the CouchDB database"
• The International School for AstroParticle Physics (ISAPP) (Jul 27^th - Aug 6^th 2013), Stockholm:
  Poster: "The EDELWEISS muon veto: achievements and improvements"
• Workshop "Data Analysis and Detector Technologies of the HAP Dark Universe" (Nov 18^th – Nov 23^rd 2012), Burg Liebenzell:
  Talk: "Calibration and monitoring of the muon veto system"

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?
  

Teaching

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

• KSETA work report 2013
• KSETA work report 2013
• KSETA work plan: description of research goals