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The search of dark matter with ArDM detector

CRACOW EPIPHANY CONFERENCE ON NEUTRINOS AND DARK MATTER 5 - 8 January 2006, Cracow, Poland. The search of dark matter with ArDM detector. Piotr Mijakowski The Andrzej Sołtan Institute For Nuclear Studies (IPJ), Warsaw, Świerk. OUTLINE. I ArDM ( Ar gon D ark M atter)

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The search of dark matter with ArDM detector

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  1. CRACOW EPIPHANY CONFERENCEON NEUTRINOS AND DARK MATTER5 - 8 January 2006, Cracow, Poland The search of dark matter with ArDM detector Piotr Mijakowski The Andrzej Sołtan Institute For Nuclear Studies (IPJ), Warsaw, Świerk

  2. OUTLINE I ArDM (Argon Dark Matter) II Neutron background in dark matter underground searches IIIGeant4 neutron background studies Young Researchers Session, 8 January 2006, Cracow

  3. part I – ArDM http://neutrino.ethz.ch/ArDM A.Badertscher, R.Chandrasekharan, L.Kaufmann, A.Knecht, L.Knecht, M.Laffranchi, M.Messina, G.Natterer, P.Otiougova, A.Rubbia, J.Ulbricht ETH Zurich, Switzerland C.Amsler, C.Regenfus, A.Buechler-Germann Zurich University, Switzerland A.Bueno, M.C.Carmona-Benitez, J.Lozano-Bahilo, S.Navas-Concha University of Granada, Spain I.Gil-Botella, P.Ladron de Guevara, L.Romero CIEMAT, Spain T.Kozłowski, P.Mijakowski, E.Rondio Soltan Institute (IPJ) Warsaw-Świerk, PolandH.Chagani, E.Daw,  P.Majewski, V.Kudryavtsev, N.SpoonerUniversity of Sheffield, England ArDM: a proposed ton-scale liquid Argon experiment for direct detection of Dark Matter as WIMPs (Weakly Interacting Massive Particle, c) Young Researchers Session, 8 January 2006, Cracow

  4. detector design LEM Ar(10 cm) drift field ≈ 4 kV/cm 170 cm LAr(120 cm) PMTs ArDM (cont.) Elastic scattering reaction: c + Arat rest c + Arrecoil • Measurement of the recoils of target nuclei [10-100 keV]. • Recoil energy  scintillation & ionization of ArgonGOAL: independently detect the light (PMTs) and the charge (Large Electron Multiplier) • light/charge ratio allows to discriminate background events (e/g vs. nuclear recoils) ArDM@CERN Young Researchers Session, 8 January 2006, Cracow

  5. ArDM status R&D @ CERN (1 ton prototype): • High voltage system • LEM based charge readout • Light detection system (PMTs + VUV reflecting mirrors) • CAD design and assemby of the detector KEY POINT: UNDERSTAND THE DETECTOR PERFORMANCE FIRST GOAL: proof of principle: 39Ar rejection (intrinsic background, beta-emitter with decay rate of ≈ 1 kHz in a 1 ton detector) Simulations: full detector geom., experimental background Young Researchers Session, 8 January 2006, Cracow

  6. ArDM prospects TIME SCALE: • 2006: assembly of detectoratCERN;test on surface • 2007: transport to the Underground Laboratory (Canfranc, Spain); installation in experimental hall and mounting of infrastructure +neutron shield • 2007: first data taking CANFRANC LAB (2450 m w.e.) pictures: E.Coccia@TAUP05 Young Researchers Session, 8 January 2006, Cracow

  7. Estimated event rates ≈ 100 event/ton/day Assuming 30 keV recoil energy threshold, Mc = 100 GeV/c2 ≈ 1 event/ton/day for s = 10-46:≈ 1 event/ton/100 day Young Researchers Session, 8 January 2006, Cracow

  8. part II – Neutron background Background events: • the same signal from WIMP & neutron interactions !!! • only possible way to distinguish: neutron multiple scattering e-like eventspossible to discriminate nuclear events MOTIVATION: neutron background limits detector sensitivity to WIMPs • NEUTRON BACKGROUND SOURCES: • local radioactivity (surrounding rock, detector components) • muon-induced neutrons • spontaneous fission 238U • (a,n) reactions; a’s from radioactive chains of U/Th Young Researchers Session, 8 January 2006, Cracow

  9. Neutron background sources 1 neutrons from surrounding rock - 238U and (a,n) reactionsflux: Frock ~ 3.8 × 10-6 n/(s·cm2) @ CANFRANC ArDM input (preliminary): ~ 13200 n/day supression: neutron shielding 2 neutrons from det. components - 238U and (a,n) reactionsflux: „detector dependent”ArDM input (preliminary): ~ 74 n/daysupression: high-purity materials 3 muon-induced neutrons – production in hadronic & e-m cascades init. by m’sflux: Fm-ind ~ 1.7 × 10-9 n/(s·cm2) @ CANFRANCArDM input (preliminary): ~ 6 n/day supression: active veto Young Researchers Session, 8 January 2006, Cracow

  10. Neutron background energy spectra [1] rock [3] m-ind [2] detector components only fission spectrum plots 1 & 3 : M.J. Carson, J.C. Davies et al., Astroparticle Physics 21(2004) 667-687 Young Researchers Session, 8 January 2006, Cracow

  11. part III – Geant4 neutron background studies How many neutron recoils we will have in our experiment? (how many neutrons will enter the detector? what energy spectrum? how many would interact and produce visible recoils? how many would undergo multiple scattering?) full detector sim. (GRANADA) ArDM simulation tasks: • detailed detector geom. (Geant4) • verifiaction of sim. processes (elastic scattering, neutron capture) • rock neutrons • neutrons from det. components • muon-induced neutrons • other background sources: g’s, 39Ar Young Researchers Session, 8 January 2006, Cracow

  12. Geant4 neutron background studies – elastic scattering in liquid Argon Argon recoil spectra from G4 simulation Tn = 2 MeV Tn = 5 keV Tn = 15 MeV Tn<<Mnnon relativistic Young Researchers Session, 8 January 2006, Cracow

  13. INPUT neutrons from rock input energy spectrum Geant4 neutron background studies – rock neutrons analysis example SIMULATION: - neutron source placed randomly on the walls of fiducial volume - neutrons going out of the detector are neglected Fn = 3.8•10-6 n/(s·cm2) assumed total neutron flux at the walls of fiducial volume OUTPUT IN OUR GEOMETRY:1 neutron per ~ 6.5 sec.13200 neutrons per day 10 keV threshold Young Researchers Session, 8 January 2006, Cracow

  14. Geant4 neutron background studies – rock neutrons analysis example Pinter~57 % Pmulti~53 % assumed 2cm spatial resolution visible95% Young Researchers Session, 8 January 2006, Cracow

  15. Summary & Outlook • ArDM: a new project aiming at developing and operating a 1 ton-scale liquid Argon detector for direct detection of WIMPs • With a 1 ton prototype we want to show the validity of this design (in particular 39Ar rejection) • Neutron shieldings will be addressed in a second phase • Investigations on neutron background sources and their interactions inside the detector are also performed (simulations in Geant4): • evaluation of expected number of neutron events (data analysis) • simulations will help to specify requirements for detector veto and shielding SIMULATIONS OUTLOOK: • Energy spectra and flux of incoming neutrons • Detailed detector geometry in Geant4 Young Researchers Session, 8 January 2006, Cracow

  16. BACKUP

  17. Geant4 neutron background studies – neutron capture in liquid Argon capture on natural Argon(40Ar - 99,6%, 36Ar - 0.337%, 38Ar - 0.063%) 6.099 MeV Initial neutron energy = 10 eV 6.598 MeV 8.788 MeV Average number of g’s produced = 3.5 Young Researchers Session, 8 January 2006, Cracow

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