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The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination

The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination. Hasko Stenzel. The LHC. pp s = 14 TeV L design = 10 34 cm -2 s -1 (after 2009) L initial  few x 10 33 cm -2 s -1 (until 2009)

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The ATLAS experiment The ATLAS Detector Physics at the LHC Luminosity determination

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  1. The ATLAS experiment • The ATLAS Detector • Physics at the LHC • Luminosity determination Hasko Stenzel

  2. The LHC • pp s = 14 TeV Ldesign = 1034 cm-2 s-1 (after 2009) Linitial  few x 1033 cm-2 s-1 (until 2009) • Heavy ions (e.g. Pb-Pb at s ~ 1000 TeV) TOTEM (integrated with CMS): pp, cross-section, diffractive physics ATLAS and CMS : general purpose TOTEM 27 km LEP ring 1232 superconducting dipoles B=8.3 T ALICE : ion-ion, p-ion LHCb : pp, B-physics, CP-violation H.Stenzel, January 2007

  3. An Aerial View of Point-1 H.Stenzel, January 2007

  4. The ATLAS Detector Calorimetry: Tracking: • Tracking (||<2.5, B=2T): -- Si pixels and strips -- Transition Radiation Detector (e/ separation) • Calorimetry (||<5): -- EM : Pb-LAr with Accordion shape -- HAD: Fe/scintillator (central), Cu/W-LAr (fwd) • Muon Spectrometer (||<2.7): air-core toroids with muon chambers Length : ~45 m Radius : ~12 m Weight : ~ 7000 tons Electronic channels : ~ 108 ~ 3000 km of cables H.Stenzel, January 2007

  5. Magnet System Central Solenoid 2T field with a stored energy of 38 MJ Integrated design within the barrel LAr cryostat H.Stenzel, January 2007

  6. Magnet System Toroid Barrel Toroid parameters 25.3 m length 20.1 m outer diameter 8 coils 1.08 GJ stored energy 370 tons cold mass 830 tons weight 4 T on superconductor 56 km Al/NbTi/Cu conductor 20.5 kA nominal current 4.7 K working point End-Cap Toroid parameters 5.0 m axial length 10.7 m outer diameter 2x8 coils 2x0.25 GJ stored energy 2x160 tons cold mass 2x240 tons weight 4 T on superconductor 2x13 km Al/NbTi/Cu conductor 20.5 kA nominal current 4.7 K working point H.Stenzel, January 2007

  7. Inner Detector The Inner Detector (ID) is organized Into four sub-systems: Pixels (0.8 108 channels) Silicon Tracker (SCT) (6 106 channels) Transition Radiation Tracker (TRT) (4 105 channels) Common ID items H.Stenzel, January 2007

  8. PIXELS • The system consists of three barrels at average radii of ~ 5 cm, 9 cm, and 12 cm (1456 modules) and three disks on each side, between radii of 9 and 15 cm (288 modules). H.Stenzel, January 2007

  9. SILICON TRACKER (SCT) • The SCT system is designed to provide eight precision measurements per track • It is constructed using 4088 silicon micro-strip modules arranged as 4 barrels in the central region and 2 x 9 annular wheels in the forward region • The SCT covers a pseudo-rapidity-range < 2.5 H.Stenzel, January 2007

  10. TRANSITION RADIATION TRACKER (TRT) • Straw tracker 50,000 in barrel 320,000 in endcaps • Gas Mixture Xe,CO2,O2 (70%,27%,3%) • Barrel radial coverage 56cm -107 cm • Endcap radial coverage 64cm – 103 cm • Drift time measurements • & Transition Radiation detection • Average of 36 points on a track H.Stenzel, January 2007

  11. TRT SCT Insertion of the SCT into barrel TRT Three completed Pixel disks (one end-cap) with 6.6 M channels H.Stenzel, January 2007

  12. LAr and Tile Calorimeters Tile barrel Tile extended barrel LAr hadronic end-cap (HEC) LAr EM end-cap (EMEC) LAr EM barrel LAr forward calorimeter (FCAL) H.Stenzel, January 2007

  13. Barrel Endcap Forward H.Stenzel, January 2007

  14. Muon Spectrometer Instrumentation The Muon Spectrometer is instrumented with precision chambers and fast trigger chambers A crucial component to reach the required accuracy is the sophisticated alignment measurement and monitoring system Precision chambers: - MDTs in the barrel and end-caps - CSCs at large rapidity for the innermost end-cap stations Trigger chambers: - RPCs in the barrel - TGCs in the end-caps H.Stenzel, January 2007

  15. End-cap muon chamber sector preparations ‘Big Wheel’ end-cap muon MDT sector assembled in Hall 180 Altogether 72 TGC and 32 MDT ‘Big-Wheel’ sectors have to be assembled ‘Big Wheel’ end-cap muon TGC sector assembled in Hall 180 H.Stenzel, January 2007

  16. The large-scale system test facility for alignment, mechanical, and many other system aspects, with sample series chamber station in the SPS H8 beam Shown in this picture is the end-cap set-up, it is preceded in the beam line by a barrel sector H.Stenzel, January 2007

  17. ATLAS online follow online what happens at http://atlas.web.cern.ch/Atlas H.Stenzel, January 2007

  18. Signal expected in ATLAS after 1 year of LHC operation Physics example H  ZZ  4  “Gold-plated” channel for Higgs discovery at LHC Simulation of a H   ee event in ATLAS H.Stenzel, January 2007

  19. Physics processes at the LHC PDFs partonic cross section H.Stenzel, January 2007

  20. Physics with ATLAS Search for the Standard Model Higgs boson over ~ 115 < mH < 1000 GeV Search for physics beyond the SM (Supersymmetry, q/ compositeness, leptoquarks, W’/Z’, heavy q/, Extra-dimensions, mini-black holes,….) in the TeV-range Precision measurements : -- W mass -- top mass, couplings and decay properties -- Higgs mass, couplings, spin (if Higgs found) -- B-physics (complementing LHCb): CP violation, rare decays, B0 oscillations -- QCD jet cross-section and as -- W/Z cross sections (+jets) Extensions of the physics program -- heavy ion running, phase transition to q/g plasma -- diffraction & forward physics H.Stenzel, January 2007

  21. Physics of the first years Expected event rates at production in ATLAS at L = 1033 cm-2 s-1 Process Events/s Events for 10 fb-1Total statistics collected at previous machines by ‘07 W e 15 108 104 LEP / 107 Tevatron Z ee 1.5107107 LEP 1107104 Tevatron 1061012–1013109 Belle/BaBar ? H m=130 GeV 0.02105 ? m= 1 TeV 0.001104--- Black holes 0.0001103--- m > 3 TeV (MD=3 TeV, n=4) H.Stenzel, January 2007

  22. Higgs Physics Search for the Higgs Boson, study of the electroweak SU(2)xU(1) symmetry breaking -- discovery of the Higgs boson & mass determination -- measurement of the Higgs couplings to verify the mass generation mechanism -- determination of the Higgs parameters (width, spin, parity, Charge (MSSM),...) coupling to fermions ~ mf /v coupling to Bosons ~ mv2/v Need to measure both H-> ff and H-> VV channels! H.Stenzel, January 2007

  23. Higgs production H.Stenzel, January 2007

  24. SM Higgs cross section H.Stenzel, January 2007

  25. Higgs Decays H.Stenzel, January 2007

  26. Higgs-> γγ H.Stenzel, January 2007

  27. Higgs-> ZZ -> 4l H.Stenzel, January 2007

  28. Higgs-> WW -> 2l2ν H.Stenzel, January 2007

  29. VBF H->ττ H.Stenzel, January 2007

  30. Higgs discovery potential H.Stenzel, January 2007

  31. Higgs couplings Relative precision on the measurement of HBR for various channels, as function of mH, at Ldt = 300 fb–1. The dominant uncertainty is from Luminosity: 10% (open symbols), 5% (solid symbols). (ATLAS-TDR-15, May 1999) Large uncertainty contribution from Luminosity! H.Stenzel, January 2007

  32. Methods of Luminosity measurements Absolute luminosity • from the parameters of the LHC machine • rate of ppZ0/W± l+ l-/lν • rate of ppγγμ+ μ- • Optical theorem: forward elastic+ total inelastic rate, extrapolation t0 (but limited |η| coverage in ATLAS) • cross-check with ZDC in heavy ion runs • from elastic scattering in the Coulomb region • combinations of all above Relative luminosity • LUCID Cerenkov monitor, large dynamic range, excellent linearity ATLAS aims for 2-3% accuracy in L H.Stenzel, January 2007

  33. Luminosity from elastic scattering H.Stenzel, January 2007

  34. Roman Pots for ATLAS RP RP RP RP 240m 240m IP RP RP RP RP MAPMTs FE electronics & shield PMT baseplate optical connectors scintillating fibre detectors glued on ceramic supports 10 U/V planes overlap&trigger Roman Pot Unit Roman Pot H.Stenzel, January 2007

  35. Roman Pot location H.Stenzel, January 2007

  36. The scintillating fibre tracker H.Stenzel, January 2007

  37. detector prototypes for testbeam 2006 2 x 2 x 30 overlaps 2 x 2 x 64 construction studies 10 x 2 x 16 resolution studies • Fabrication of prototypes at CERN • with support from Lisbon (LIP) for • fibre machining, aluminum coating, QC • testbeam mechanics • and from Giessen for • gluing of fibres • optical connectors • Plan to produce a full-scale prototype in 2007 • (1/8 of the full set-up) H.Stenzel, January 2007

  38. Simulation of the LHC set-up elastic generator PYTHIA6.4 with coulomb- and ρ-term SD+DD non-elastic background, no DPE beam properties at IP1 size of the beam spot σx,y beam divergence σ’x,y momentum dispersion ALFA simulation track reconstruction t-spectrum luminosity determination later: GEANT4 simulation beam transport MadX tracking IP1RP high β* optics V6.5 including apertures H.Stenzel, January 2007

  39. Simulation of elastic scattering hit pattern for 10 M elastic events simulated with PYTHIA + MADX for the beam transport t reconstruction: • special optics • parallel-to-point focusing • high β* H.Stenzel, January 2007

  40. acceptance distance of closest approach to the beam Global acceptance = 67% at yd=1.5 mm, including losses in the LHC aperture. Require tracks 2(R)+2(L) RP’s. Detectors have to be operated as close as possible to the beam in order to reach the coulomb region! -t=6·10-4 GeV2 decoupling of L and σTOT only via EM amplitude! H.Stenzel, January 2007

  41. t-resolution The t-resolution is dominated by the divergence of the incoming beams. σ’=0.23 µrad ideal case real world H.Stenzel, January 2007

  42. L from a fit to the t-spectrum Simulating 10 M events, running 100 hrs fit range 0.00055-0.055 large stat.correlation between L and other parameters H.Stenzel, January 2007

  43. experimental systematic uncertainties • Currently being evaluated • beam divergence • detector resolution • acceptance • alignment • beam optics • background • ΔL/L ≈ 2.8-3.2 % H.Stenzel, January 2007

  44. conclusion • LHC start up in 2007 • ATLAS detector on track • running at low luminosity 1033cm -2s-1 and in 2008 • switch to design luminosity 1034cm -2s-1 after 2009 • luminosity calibration from elastic scattering in 2009 ? H.Stenzel, January 2007

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