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Investigation of the muon-induced background of the EDELWEISS-II experiment

Investigation of the muon-induced background of the EDELWEISS-II experiment. Astrid Chantelauze KIT – Karlsruhe Institute of Technology Université Blaise Pascal. Evidences of dark matter Strategies of detection Direct detection: EDELWEISS-II experiment

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Investigation of the muon-induced background of the EDELWEISS-II experiment

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  1. Investigation of the muon-induced background of the EDELWEISS-II experiment Astrid Chantelauze KIT – Karlsruhe Institute of Technology Université Blaise Pascal 1 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  2. Evidences of dark matter Strategies of detection Direct detection: EDELWEISS-II experiment Investigation of the muon-induced background: Muon veto performances Muon veto – bolometer coincidence analysis Overview 2 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  3. Eppur si muove Hello! Barred Spiral Milky Way Illustration, Credit: NASA/JPL-Caltech/R. Hurt (SSC) Since 6 centuries… 3 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  4. Rotation of spiral galaxiesUsing movement to measure mass Vera Rubin (70s) showed that observation of rotation of disks in their outer parts required a lot of invisible mass … M33, Orange Observatory E. Corbelli & P. Salucci MNRAS, 311, 441 (1999) 4 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  5. Image 1 Object Cluster Image 2 Gravitational lensing ΩM= 1 ΩM= 0.3 Galaxy Cluster Abell 2218 as seen by the observer Observer N. A. Bahcall et al., Astrophysical Journal, 447, L81(1995) 5 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  6. LCDM ΩΛ Ωnon-b Ωb ΩΛ ΩM New order of the universe: Ωtot = ΩΛ + ΩM + Ωk Ωk = 0.01 flat universe G. Hinshaw et al., Astrophysical Journal, 170, 288 (2007) S. Perlmutter, Physics Today, 56, 53 (2003) 6 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  7. LCDM ΩΛ Ωnon-b Ωb ΩΛ ΩM S. Perlmutter, Physics Today, 56, 53 (2003) New order of the universe: Ωtot = ΩΛ + ΩM + Ωk Ωtot = ΩΛ + ΩM + Ωk = 1.011 ± 0.012 7 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  8. 4% 20% as new unknown particles ! 8 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  9. 4 main facts about its nature: non-baryonic weakly interacting essentially stable, or at least have a life time long compared to the present age of the universe cold = read slow-moving. More precisely, a cold dark matter candidate must be non-relativistic throughout the formation of largescale structure Dark Matter particle freeze-out of a weakly interacting massive (WIMP) when reaction rate drops below expansion rate time t (t ~ T-2) increasing <sAv> thermodynamic equilibrium x = mc / T Tfreeze-out~ 1/20· Mc E. W. Kolb & M. S. Turner, The Early Universe, Frontiers in Physics, Vol. 69 (1990) 9 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  10. Dark Matter in a cloud around the milky way WIMP WIMP 200 cm³ Galactic WIMP halo ≈72 Ge • Lightest Supersymmetric Particle (LSP) • mass 50 GeV to ~ 1000 GeV • relative speed 270 km/s (~ our orbital velocity around galactic center) • only a few keV of recoil energy • cross section • local WIMP-density sc < 10-42cm2 rc 0.3 GeV/cm3 (1 per cup) • very very rare scattering events (< 1 / week / kg) in the same cup 60.000 ν 10 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  11. 11 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  12. c 72Ge Dark Matter search Indirect DM search (cc annihilation) cc ff needs astrophysical overdensities: 1. galactic center excess of cosmic rays (g´s & antimatter) 2. the Sun  energetic “solar” neutrinos (ne, nm, nm) 3. the Earth  “upward-going” muons from (nm, nm) Production at Accelerators Heavy strongly-interacting SUSY states (squarks, gluinos) produced copiously in p-p collisions  missing transverse momentum Direct dark matter elastic scattering on a nucleus 1. annual modulation 2. event-by-event discrimination 12 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  13. WIMP Direct DM search – detection schemes …via elastic scattering off nuclei Ge, CF3I, C4F10 Ge, Si Ionization CoGeNT COUPP Picasso Edelweiss, CDMS 10% energy WArP, ArDM Heat Al2O3, LiF liquid Xe/Ar Target 100% energyslowestcryogenics CRESST-1 Zeplin-3 , LUX, Xenon-10/100 Light NaI, liquid.Xe 1% energyfastestno surface effects CaWO4, BGO DAMA, Libra, Zeplin-1, XMASS, KIMS, ANAIS CRESST-2 WIMP 13 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  14. EDELWEISS @ Laboratoire Souterrain de Modane FRANCE ITALIE Altitudes 1228 m 1263 m 1298 m Distances 6210 m 12 868 m 0 m 14 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  15. 300 Heat 200 100 0 0 100 200 300 400 500 t (ms) Ionisation 100 0 0 2 4 6 8 10 t (ms) Germanium bolometers Guard ring NTD sensor m = 320g Center electrode • Simultaneous measurement •  Heat @ 17 mK with Ge/NTD thermometer •  Ionization @ few V/cm with Al electrodes •  Evt by evt identification of the recoil by ratio Q = Eionization / Erecoil • Q = 1 for electronic recoil • Q  0.3 for nuclear recoil 15 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  16. Standard Q-plot calibration of a 320g Ge bolometer with 252Cf 73Ge(n,n’g) 68.8 keV 13.3 keV n/g discrimination > 99.9% for Er >15 keV Recoil threshold 20 keV Ionization threshold 3.7 keV O. Martineau et al., NIM A, 530, 426 (2004) 16 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  17. The Edelweiss experiment One Germanium detector Some layers of detectors The cryostat when it’s closed The shielding of the experiment 17 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  18. EDELWEIS-II muon veto system • 42 modules covering 100 m2 98% coverage • energy, timing µ tracking capability • modular structure • read at both side 18 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  19. Muon veto – Life time position known thanks to user position known via laser meas. “veto closed” “veto open” July 2006 – July 2009: 835.9 live days = 76%; 85% of data “closed” 19 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  20. Muon candidates • Muon candidates: • Internal coincidence within a module • strictly more than one module hit • coincidence of two modules of different levels (module #4 and lower level) m 20 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  21. Muon rate Geant-4 simulation M.Horn, PhD thesis 21 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  22. Through going muons m High multiplicity events → showers • expected time difference (vertical tracks): Dt = 5.2m / 3×108 m/s ≈ 17 ns • obtained from the fit: Dt ≈ 19 ± 2 ns →Δl = 5.7 ± 0.6 → non vertical • but still “downward going muons” 22 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  23. Coincidence analysis Muon track Ionization / Heat removed ! Heat Region of interest for WIMP signals Heat 23 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  24. Coincidence analysis with Run 8 24 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  25. Run 8 – Distribution of the time as viewed in the muon veto Time restarts with each run… … perfectly continuous during a run Connect correct veto period to run of s2 + same uncorrelated structure for other comput. → reconstrution of continuous a time line for all sub-systems 25 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  26. Run 8 – Bolometer event building ∆tbolo > 500 ms 26 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  27. Muon veto-bolometers coincidences ∆tbolo > 500 ms > 1 veto module hit Define an interval at tveto - tbolo = +25 ± 10 ms 27 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  28. ∆tbolo > 500 ms Run 8 – Systematics of the muon veto-bolometers coincidence interval > 1 veto module hit Time interval Low energy High energy Total excess coincidence interval for Run 8 tveto - tbolo in [+15, +35] ms 28 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  29. Erecoil < 250 keV Erecoil ≥ 250 keV measured events 16 28 expected accidentals 3.7 ± 0.2 2.9 ± 0.2 excess coincidences 12.3 ± 4.2 25.1 ± 5.5 signal/background 3.3 ± 1.4 8.7 ± 2.4 ∆tbolo > 500 ms Run 8 – Coincidences at ER < 250 keV > 1 veto module hit 4 events at low Er, low Q: (Er = 19 keV, Q = 0.26) (Er = 23 keV, Q = 0.17) (Er = 26 keV, Q = 0.23) (Er = 36 keV, Q = 0.31) Erecoil < 250 keV Muon-induced event rate: 0.04 events/kg.d 29 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  30. Run 8 – Comparison with the simulation • 16 bolometers non compact • 15 keV < Edep < 250 keV • Single bolometer events Erecoil < 250 keV Measured: 0.04 events/kg.d Expected from Geant4 simulation: ~ 0.03 events/kg.d Geant-4 simulation M.Horn, PhD thesis hits/crystal (1/keV/day) • Compact geometry 120 bolometers • 1 keV < Edep < 250 keV • Multi hits 30 Energy deposit in bolometers/hit (keV) 30 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  31. ∆tbolo > 500 ms Run 8 – Coincidences at ER ≥ 250 keV > 1 veto module hit Erecoil ≥ 250 keV coincidences with ● multi(bolo) = 1 ■ multi(bolo) > 1 and if multi(bolo) > 1 ∆ individual bolometer 3 events at low Er, low Q: (Er = 16 keV, Q = 0.22) (Er = 34.9 keV, Q = 0.47) (Er = 35 keV, Q = 0.33) Erecoil ≥ 250 keV Muon-induced event rate: 0.1 events/kg.d 31 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  32. 32 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  33. Run 8 Run 10 33 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  34. Characteristics of Run 8 and Run 10 34 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  35. New time stamp from the OPERA box as viewed in the muon veto almost perfect Removing time mismatches: 10-3 jumps 35 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  36. Characteristics of Run 8 and Run 10 36 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  37. Run 10 - Events in the ntp file: Biplot heat vs ionization s1 Events which pass the adaptative threshold Events which pass the adaptative threshold Events which have ΣEH > 30 keV and ΣEI > 30 keV 37 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  38. Characteristics of Run 8 and Run 10 0.0107 Hz 38 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  39. Run 10 – Bolometer event building Events with ΣEH > 30 keV and ΣEI > 30 keV ∆tbolo > 500 ms 39 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  40. Run 10 – Muon veto-bolometers coincidences Events with ΣEH > 30 keV and ΣEI > 30 keV ∆tbolo > 500 ms > 1 veto module hit Define an interval at tveto - tbolo = -5 ± 5 ms 40 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  41. Run 10 – Evaluation of the muon veto-bolometer coincidence interval Time interval Low energy High energy Total excess coincidence interval for Run 10 tveto - tbolo in [-15, +5] ms Events with ΣEH > 30 keV and ΣEI > 30 keV ∆tbolo > 500 ms > 1 veto module hit 41 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  42. Run 10 – Coincidences at EH < 250 keV Events with ΣEH > 30 keV and ΣEI > 30 keV ∆tbolo > 500 ms > 1 veto module hit Signal / Background = 2.4 Quality of coincident events Erecoil < 250 keV 0 events at low EH, low Q ! Muon-induced event rate: 0.023 events/kg.d 42 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  43. Run 10 – Coincidences at EH ≥ 250 keV Events with ΣEH > 30 keV and ΣEI > 30 keV ∆tbolo > 500 ms > 1 veto module hit EHeat ≥ 250 keV coincidences with ● multi(bolo) = 1 ■ multi(bolo) > 1 and if multi(bolo) > 1 ∆ individual bolometer EHeat ≥ 250 keV 1 event at low EH, low Q: (EH = 294,2 keV, Q = 0.41) in coincidence with (EH = 151.1 keV, Q = 1.08) Muon-induced event rate: 0.1 events/kg.d Signal / Background = 9.1 43 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  44. Muon veto allows to access the muon event topology (tracking in time and energy) and the muon flux Firstcombined analysis of both muon veto and bolometers Identification of muon-induced events: ER< 50 keV …………. dominated by neutrons 50 < ER < 250 keV …. electron like single hits ER > 250 keV ……….. multi-bolometer events with single low-Q hits Muon-induced events at ER<250 keV, for the EDW-II experiment: G = 0.04 events/kg.d New EDW bolometer (ID) – e/gbackground free EURECA: joint effort of CRESST and EDW – 1 ton scale Non vetoed µ-induced bg would be the limiting background Summary 44 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  45. Investigation of the muon induced background of the EDELWEISS-II experiment Astrid Chantelauze KIT – Karlsruhe Institute of Technology Université Blaise Pascal 45 | Astrid Chantelauze | PhD defense | Université Blaise Pascal | 04/11/09

  46. 25 ms 46 | Astrid Chantelauze | IK-Institutsseminar | KIT | 17/11/09

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