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  1. Muon Reconstruction in ATLAS Georgios StavropoulosU.C. Berkeley LBNL 20 May 2005

  2. Contents • The knows and the whys in H.E.P. • LHC andATLAS description • The ATLAS Muon Spectrometer • Muon Reconstruction and Identification • ATLAS potential to discover the SM Higgs. G. Stavropoulos

  3. Elementary Particles Fermions: Spin ½. G. Stavropoulos

  4. The Forces in Nature Bosons: Spin 0, 1, 2. G. Stavropoulos

  5. Open Questions Are really elementary the “elementary” particles? Why do they have these mass and charge values? Why so many forces? The Graviton exists? Are they other undiscovered particles in Nature? Why 3 generations? Why …… ? G. Stavropoulos

  6. The Standard Model and Beyond • Today, the most successful theoretical model, explaining lots of experimentaldata. Predicted the existence of the W±, Z0 particles. • Predicts the existence of one more neutral particle, the Higgs. Experimental measurements confirm that Higgsshould have, if it exists, mass > 114 GeV • But, leaves a lot open questions • Why these particles masses? • Gravity? • If neutron have mass; • Beyond the Standard Model • GUTs • Supersymmetry • Strings • ………. G. Stavropoulos

  7. Physics studies withLHC All theories agree, that the systematic study of the physics phenomena in the energy range between 100 – 1000 GeV will answer many of our questions • Standard Model Physics - Higgs search • B-physics • Heavyquarks and leptons • QCD • Supersymmetry • Exotics • ……… G. Stavropoulos

  8. Large Hadron Collider • ~27 km circumference • pp colisions. 7 TeV beam energy (c – 10 km/h) • Bunch spacing 25 ns • Designed Luminosity 1034cm-2s-1 109 interactions/s G. Stavropoulos

  9. SM Higgs Production @ LHC Gluon Fusion - dominant process Vector Boson Fusion - 20% of gg @ 120GeV Associated Production - W or Z (1-10% of gg) Associated Production - tt or bb (1-5% of gg) - - 4 production mechanism key to measure H-boson parameters G. Stavropoulos

  10. Main Discovery Channels Dominant BR for mH<2mZ:  (H  bb)  20 pb;  (bb)  500 b for m(H) = 120 GeV • no hope to trigger or extract fully had. final states • look for final states with ,  ( = e, ) - - m(H) > 2 mZ : H  ZZ  4 qqH  ZZ    *qqH  ZZ   jj * qqH  WW jj **for mH > 300 GeV forward jet tag Low mass region: m(H) < 2 mZ : H   : small BR, but best resolution H  bb : good BR, poor resolution  ttH, WH H   : via VBF H  ZZ*  4 H  WW*   or jj : via VBF - - _ G. Stavropoulos

  11. The LHC detectors •  1 GHz interaction rate •  23 minimum bias interactions per bunch crossing (pile-up) Η → ΖΖ → 4μ Extreme demands on detectors: • high granularity • high data-taking rate • high radiation environment G. Stavropoulos

  12. The ATLAS Detector Length: ~40m Radius: ~10m Weight: ~ 7000 t El. Channels: ~108 Cables: ~3000 km Muon Detectors Fast response for trigger Good p resolution (e.g., A/H  ) For com- parison Inner Detector High efficiency tracking Good impact parameter res. (e.g., H  bb) Electromagnetic Calorimeters excellent electron/photon identification Good E resolution (e.g., Hgg) Hadron Calorimeters Good jet and ET miss performance (e.g., H ) G. Stavropoulos

  13. The ATLAS Detector (cont.) Trigger and DAQ Data Acquisition System Αnalog Signals (10 PB/s) Decisions Trigger System Raw data Mass Storage Design feedback Detector & Trigger Simulation Reconstruction & Αnalysis Physics Results G. Stavropoulos

  14. x y L θMS θ0 0 θMS Measurement of Charged Tracks L To measure a pT = 1 TeV track with 10% resolution in a magnetic field of L = 5 m and ∫Bdl = 3 Tm we should aim for a σ(χ) < 50μm detector resolution.A pT =20 GeV is measured with 0.2% accuracy in the same detector. B s ρ θ Multiple scattering contributes to themeasurement error. In a 3-layer aluminum detector, with 1 cm thicklayers, these error is calculated tobe ~0.8%. G. Stavropoulos

  15. The ATLAS Muon Spectrometer RPC και TGC: Trigger the detector and measure the muons in the xy and Rz planes with an accuracy of several mm. CSC: Measure the muonsinRz with ~80 μm accuracy and in xy with several mm. Cover 2<|η|<2.7 MDT: Measure the muonsinRz with ~80 μm accuracy. Cover|η|<2 Three toroidal magnets create a magnetic field with: • Barrel:∫Bdl = 2 – 6 Tm • Endcaps:∫Bdl = 4 – 8 Tm G. Stavropoulos

  16. muon • The MDT Chambers G. Stavropoulos

  17. An Event G. Stavropoulos

  18. Muon Reconstruction with MOORE G. Stavropoulos

  19. Muon Identification with MuID G. Stavropoulos

  20. Fakes PT /GeV Results Michela Biglietti Efficiency vs pT PT /GeV G. Stavropoulos

  21. ΔPT/PTvs PT PT /GeV Resolution 1/pΤ pull = (1/pΤrec - 1/pΤgen)/Error(1/pT) G. Stavropoulos

  22. Experimental verification of the detectors’ design characteristics A significant and very important part of the construction phase of a detector, is the experimentalverification of its design and construction characteristics. Several measurements have already been performed (or they currently happen) in cosmic andtest-beam setups, which confirm that the detector under construction will be able to deliver thequality measurements as it is requested by the ATLAS Physics program. The design characteristics that have already been experimentally verified: • Track reconstruction efficiency. • Spatial resolution • Efficiency and timing of the trigger chambers • Detector performance in high event rates. • Alignment system. G. Stavropoulos

  23. Experimental verification of the detectors’ design characteristics G. Stavropoulos

  24. width = 57 μm residual vs. drift distance EOL ML1 L1 Run 1198 [cm] Spatial Resolution • Hit Residuals: Katharina Mair drift distance [cm] G. Stavropoulos

  25. period 6.8.03: Run700334-Run700339 + From alignment system From track reconstruction Run1201 width: 172 m sagitta [cm] Alignment G. Stavropoulos

  26. # of Rec. Tracks per event And finallythe Higgs…. Invariant Massof the 4 muonsinGeV G. Stavropoulos

  27. Overall Higgs Significance L dt = 100 fb-1 VBF channels at low mass not yet included in the plot! Low mass will improve! LEP2 Limit 5s 700 GeV < mH < 1 TeV: need H  ZZ  , jj H  WW  jj 114 GeV < mH < 190 GeV: several complementary channels 190 GeV < mH < 700 GeV: easy with H  ZZ  4 G. Stavropoulos

  28. Status of MDT Production • Over 95% of the MDT chambers have been produced. • Over 85% are equipped with gas manifold and Faraday cages. • 52% of the MDT’s already at CERN. • 40% fully tested with cosmics (partly at the home institutions) as individual chambers. • 10% of the RPC/MDT stations have past the qualification tests. G. Stavropoulos

  29. Installation G. Stavropoulos