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Muon Detection at CMS: from Detector and Software Commissioning to SM Physics and Higgs discovery

Muon Detection at CMS: from Detector and Software Commissioning to SM Physics and Higgs discovery. Sara Bolognesi - Torino University and INFN. 2° year Ph.D. Seminar, February 2008. Drift Tubes: Hardware and Software Commissioning. Outline. Introduction on Muon Detector System in CMS :.

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Muon Detection at CMS: from Detector and Software Commissioning to SM Physics and Higgs discovery

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  1. Muon Detection at CMS: from Detector and Software Commissioning to SM Physics and Higgs discovery Sara Bolognesi - Torino University and INFN 2° year Ph.D. Seminar, February 2008

  2. Drift Tubes: Hardware and Software Commissioning

  3. Outline • Introduction on Muon Detector System in CMS: • barrel: Drift Tubes (DT) and Resistive Plate Chambers (RPC) • endcap: Cathode Strip Chambers (CSC) and RPC • Drift Tubes detector at work! • single cell operation principle (calibration procedure) • chamber structure and track segment reconstruction • DT Commissioning with Cosmic Muons: • Magnet Test and Cosmic Challenge in 2006 • …continuous integration/commissioning effort ever since … Sara Bolognesi 3 half PhD seminar (2008 Febr. 22 Torino)

  4. Muon detectors Barrel: 5 wheel (+/-2, +/-1,0) in h 12 sectors in f 4 DT stations (from inner MB1 to outer MB4) 6 RPC stations Endcaps: 4 disks in z 2-3 rings 18-36 trapezoidal CSC in outer rings (h<1.6) 18-36 trapezoidal RPC Magnetic field map B≈1.8T B≈4T Sara Bolognesi 4 half PhD seminar (2008 Febr. 22 Torino)

  5. m Drift Tubes • ionization (Em<1TeV, ArCO2 gas) → electron drift→avalanche at wire→signal: e- drift time measured and converted into distance (with L/R ambiguity) • drift velocity calibration: • time synchronization: Tmax distributions tmeas = telectr + t.o.f. + tprop + tdrift time pedestal (ttrig) TDC spectrum vdrift = L / (2 × <Tmax>) resolution = vdrift× <sTmax> time pedestal (ttrig) Sara Bolognesi 5 half PhD seminar (2008 Febr. 22 Torino)

  6. simulation DT chambers • 1D hit from drift time measurement: constant vdrift or vdrift = f(tdrift, a,Bwire,Bnorm). • 2D segments reconstructed in each SL pattern recognition and linear fit → L/R ambiguity solved conflicts solved and ghosts suppressed (c2, nhits) • 3D segments reconstr. in each camber r-f and r-z segments matched (all combinations) r-z residuals r-f residuals • Resolutions: simulation r-f 90mm (7mrad on angle) bending coordinate → 8 hits r-z 120mm (60mrad on angle) only 4 hits (non-Gaussian tails from d-rays) Sara Bolognesi 6 half PhD seminar (2008 Febr. 22 Torino)

  7. DT Commissioning with Cosmics Distributions on CMS surface (510m on sea level): total rate ≈ 30000 Hz (600 Hz in cavern) • CMS is not designed for cosmics! • Timing: cosmics have random arrival time while CMS trigger designed for bunched muons (40 MHz) with fixed t.o.f. → additional smearing of (25/√12) ns ≈ 400 mm correct segment (33°) real cosmic in CMS visualization: • Angular distribution: CMS (software and hardware) designed for m from IP e.g.: DT trigger < 45°, track reconstruction with vertex constraint wrong reconstructed segment (65°) Sara Bolognesi 7 half PhD seminar (2008 Febr. 22 Torino)

  8. wheel 2 wheel 1 Magnet Test and Cosmic Challenge • 3 Barrel sectors + 60° slice of adjacent Endcap: • 14 DT chambers DAQ & trigger • 21 RPC chambers • 36 CSC chambers (some tracker modules, ECAL crystals and HCAL sectors also in the DAQ) • subset of final readout and trigger electronics, global trigger and DAQ • B ramping up and down (0-4T) various times • Detector run in stable mode for more then 2 months → 230 M recorded events Sara Bolognesi 8 half PhD seminar (2008 Febr. 22 Torino)

  9. DT Commissioning & Global Runs TDC spectra Test pulse signals for a single wire trigger source: good test pulse signals electronic noise due to enabling/disabling masks • Test of calibration procedures in real life: noise e.g. integration of different sub-detectors • Monitor of the detector performances:noise, dead wire, interchannel synchronization • The full detector monitored/calibrated run by run: • high automation • robust software implementation • reliable strategy of databases production and storage Sara Bolognesi 9 half PhD seminar (2008 Febr. 22 Torino)

  10. My work on DT • I was strongly involved in • software development: calibration, local reconstruction, Data Quality Monitoring • data taking (DQM responsible at MTCC) • real and simulateddata analysis (calibration responsible in 2007): calibration, residuals, noise/dead channels • Publications: • Results of the first integration test of the CMS drift tubes muon trigger Nucl.Instrum.Meth.A579:951-960,2007. CMS NOTE-2007/034. • Offline Calibration Procedure of the Drift Tube Detectors • Measurement of Drift Velocity in the CMS Barrel Muon Chambers at the CMS Magnet Test Cosmic Challenge CMS NOTE-2008/003. • Local Muon Reconstruction in the Drift Tube Detectors CMS NOTE in publication • Test of the DT Simulation and Local Reconstruction Algorithms on the 2004 Test-Beam data CMS NOTE in preparation • The CMS Precision Muon Chamber in the Magnet Test Cosmic Challenge (MTCC). CMS NOTE in preparation Sara Bolognesi 10 half PhD seminar (2008 Febr. 22 Torino)

  11. Muon momentum scale calibration

  12. Outline • Muon reconstruction strategy in CMS • Z resonance as a tool for “physics commissioning” • Calibration of muon momentum scale exploiting the Z peak: • likelihood method based on real data and Z mass precise knowledge • effects due to realistic detector behavior (misalignment, B field distortion) • a use-case: evaluation of Z cross section systematics • future plans: resolution, low mass resonances, backgrounds Sara Bolognesi 12 half PhD seminar (2008 Febr. 22 Torino)

  13. pT resolution (barrel) Muon Reconstruction • Tracker Muons: good resolution at low pT, high background • StandAlone Muons (DT, CSC, RPC): high purity, good resolution at high pT • Global Muons (matching): STA purity and Tracker resolution Resolution results from a compromise between multiple scattering and lever arm Sara Bolognesi 13

  14. Physics Commissioning: Z→mm • “Standard candle” to measure detector performance from data and to control uncertainties and systematics: • tag&probe method → mtrigger and reconstruction efficiency • mass peak → m momentum scale calibration and resolution measurement • well known xsec → constraint on PDF and luminosity • Z @ LHC xsec × kin. accept. ≈ 0.8 nb xsec(Z→mm) ≈ 1.8 nb ≈ 8000 Z with 10 pb-1 efficiency trigger 98.1% lumi ≈ 14 pb-1 ; MC m cut: |h|<2.5, M(mm)>20 GeV Sara Bolognesi 14 half PhD seminar (2008 Febr. 22 Torino)

  15. Calibration strategy • The muon pT is modified toforce the Z peak in the right position pTcorr = k × pT NOT a simple pT shift BUT a correction as a function of muon kinematic: k = a1 + a2pT + a3|h| + a4h2 + fit Lorentzian + decr. expo. + q×a5,i sin(f +a6,i) (i=1,2) different for m+ and m- • 8 correction parameters (ai) computed maximizing a likelihood: • Micorr computed event by event using the muon momentum correction • MrefMonteCarlo or PDG value With a likelihood you can take into account the full mm kinematic for each event without averaging!! Sara Bolognesi 15 half PhD seminar (2008 Febr. 22 Torino)

  16. Generated Z mass • Lorentzian + decr. expo fit: • generated Z mass 91.13 GeV ≈ 50 MeV PDF effect fit Lorentzian + decr. expo. • generated mm mass 90.89 GeV ≈ 250 MeV Final State Radiation FSR • Results from the fit used as reference G and MZref value in the likelihood Sara Bolognesi 16 half PhD seminar (2008 Febr. 22 Torino)

  17. Reconstr. Z mass Mean 90.89 ± 0.02 Gamma 2.95 ± 0.05 STAm Mean 88.2 ± 0.2 • STAm scale bias > 10% Gamma 17.7 ± 0.4 • GLBm and Tracks scale bias 0.5% Mean 89.7 ± 0.1 Gamma 16.4 ± 0.3 • bias linear in pT and parabolic in h (no f dependence) Tracks Mean 90.89 ± 0.02 Gamma 2.95 ± 0.05 Mean 88.2 ± 0.2 Tracks Gamma 17.7 ± 0.4 Mean 89.7 ± 0.1 Gamma 16.4 ± 0.3 Sara Bolognesi 17 half PhD seminar (2008 Febr. 22 Torino)

  18. B'=B*1.02 B'=B*1.05 B'=B*1.002 Realistic detector • Scenarios with worsening of the detector behaviour: • Tracker and Muon System misaligned in 10pb-1 scenario: Tracks: additional f dependence • B field distortion: Tracks: • new little dependence on f (only 2‰ distortion) STAm: • big dependence on f (barrel yoke: 2% distortion) • new h dependence (endcap: 5% distortion) • additional correction as a function of pT (B increased => pT underestimated) GLBm: not sizeable effects Sara Bolognesi 18 half PhD seminar (2008 Febr. 22 Torino)

  19. Systematics on Z cross section Z reconstructed with GLBm+GLBm, GLBm+Tracks, GLBm+STAm to maximize efficiency, standard selection cuts applied on pure signal sample • Muon momentum scale systematics: GLBm+Track+STAm 2.7% GLBm+Track 0.03% • Other systematics: • Tracker misalignment: • 3.5% without corrections • 0.9% after corrections • Muon System misalignment: • 3.2% without corrections • 0.3% after corrections • B field misknowledge: • 1.8% without corrections • 0.5% after corrections Sara Bolognesi 19 half PhD seminar (2008 Febr. 22 Torino)

  20. Future plans • Improve the likelihood convolving resolution function (Gaussian with asymmetric queue) resolution = Gaussian resolution = Crystal Ball c2 = 3.4 c2 = 1.2 FSR effect well fitted s = 1.08±0.05 GeV s = 1.15±0.05 GeV FSR • Extract also the muon resolution as a function of muon kinematic • Study low mass resonances (J/y, U) to calibrate low pT muons consider background in the likelihood (from sidebands) Sara Bolognesi 20 half PhD seminar (2008 Febr. 22 Torino)

  21. H→gg, MH = 100 GeV H→ZZ→4e, MH = 150 GeV Plans for H→ZZ→mmnn H→ZZ→4m, MH = 150 GeV

  22. Higgs @ LHC PRODUCTION DECAY excluded by LEP Sara Bolognesi 22 half PhD seminar (2008 Febr. 22 Torino)

  23. n n g Z n Z H V H n m g m V Z Z m m MH Nev(1 fb ≈ start-up year) 150 GeV 30 200 GeV 59 500 GeV 15 New channel : H→ZZ→mmnn • Leptonic final states favored inside the big hadronic background at LHC H→gg for low Higgs mass H→ZZ→4l “golden channel” H→WW→lnln most promising @ 160GeV • Not yet considered: s≈ 50 fb s≈ 9 fb quite high BR ≈ 10 × BR(4m) • Difficult to work with MET: good detector control needed; high DY background Sara Bolognesi 23 half PhD seminar (2008 Febr. 22 Torino)

  24. H→ZZ→mmnn analysis strategy • Main backgrounds: ttbar → bbmmnns≈ 9.4 pb → big s (QCD process) WW → mnmns ≈ 1.3 pb → irreducible ZZ → mmnns≈ 0.10 pb WZ → mnmms≈ 0.25 pb → high m efficiency needed → MET resolution is crucial!! Drell-Yan (+jets) → mm(+jets)s≈ 65 pb • Ask for • exactly 2m with high pT (>20 GeV) in barrel region with opposite charge and M(mm) ≈ MZ ATLAS significance (3years low lumi) • high MET = pTZ (big for high MH) • central jet veto • kinematical cuts: • single Z has lower pT, • ZZ more soft and less central (same for m from ttbar), • WW are back-to-back → lower MET, • b-tagging against ttbar • Analysis cuts as a function of MH → maximum significance for right MH Sara Bolognesi 24 half PhD seminar (2008 Febr. 22 Torino)

  25. Publications on Z and H W and Z bosons physics at LHC at low luminosity. IFAE proceedings: Pavia 2006, High energy physics Towards a measurement of the inclusive W→mn and Z→m+m- cross sections in pp collisions at √s = 14 TeV. CMS Analysis Note,CMS-AN 2007/031 CMS technical design report, volume II: Physics performance. J.Phys.G34:995-1579,2007. Boson-boson scattering and Higgs production at the LHC from a six fermion point of view: Four jets + l nu processes at O( alpha(em)**6 ). JHEP 0603:093,2006, e-Print: hep-ph/0512219 Workshop on CP Studies and Non-Standard Higgs Physicse-Print: hep-ph/0608079 Les Houches physics at TeV colliders 2005, standard model and Higgs working group: Summary report.e-Print: hep-ph/0604120 HERA and the LHC: A Workshop on the implications of HERA for LHC physics. Proceedings, Part A.HERA and the LHC: A Workshop on the implications of HERA for LHC physics: Proceedings Part B. CERN-2005-014, DESY-PROC-2005-01, e-Print: hep-ph/0601013 + e-Print: hep-ph/0601012 Study of VV-scattering processes as a probe of electroweak symmetry breaking. CMS Analysis Note, CMS-AN 2007/005 Higgs at CMS with 1, 10, 30 fb-1. 2007 International Linear Collider Workshopproceedings to be published Workshop sui MonteCarlo la Fisica e la Simulazione a LHC.Proceedings in preparation Sara Bolognesi 25 half PhD seminar (2008 Febr. 22 Torino)

  26. The end. Thanks! Back-up slides

  27. Drift Tube non-linearities TDC spectrum TDC spectrum • Angular effects: m half cell test beam (0°) test beam (30°) e- • Magnetic field effects: Residuals simulation (wh+/-2) reconstr. with constants vdrift A parameterization of the cell response can be used: vdrift = f(tdrift, a,Bwire,Bnorm). Sara Bolognesi half PhD seminar (2008 Febr. 22 Torino) 27

  28. Drift Tubes in real life! half cell d rays: high energy e- knocked out from atoms by the m Residuals e- m simulation e- shorter drift time m after-pulses: primary e- produce g that can extract secondary e- from cell wall half cell e- e- g secondary signals after Tmax TDC spectrum test beam tsecondary - tprimary Other effects: MTCC (a),(f) random electronic noise (b),(e) pile-up hits from muons in other bunches of the beam (d) after-pulses (c) signal region Sara Bolognesi 5 half PhD seminar (2008 Febr. 22 Torino)

  29. ttrig calibration MB1 MB2 MB3 MB4 W2 W2 W2 W1 W1 W2 W1 W1 W2 W1 10 11 14 14 10 10 11 10 10 11 10 10 10 11 TOF effect (10 ns) MB1 MB2 MB3 MB4 • ttrig for two MTCC runs: B off (local run) B = 3.8 T (global run) • ttrig for two trigger configuration: Tmean [nsec] Shift ~ 28 BX Technical Trigger Default Cosmic 1-> 12 1-> 12 1-> 12 1-> 12 Station & Sector Sara Bolognesi 29 half PhD seminar (2008 Febr. 22 Torino)

  30. Meantimer computation • It’s the average Tmax mediated on the whole semicell: (most simple case) Tmax distributions (“meantimer”) • Different formulas for different track patterns Sara Bolognesi 30 half PhD seminar (2008 Febr. 22 Torino)

  31. vdrift calibration SL theta SL phi for each SL vdrift(Boff) - vdrift(Bon) ~2% vdrift(Boff) MB1 MB2 MB3 MB4 W2 W2 W1 W1 W2 W2 W1 W1 W1 W2 14 14 10 10 11 10 10 11 10 10 11 10 10 11 B off (local run) B = 3.8 T (global run) vdrift for each SL MB1 MB2 MB3 MB4 W2 W1 W2 W1 W2 W1 W2 W1 W2 W1 10 11 10 10 11 10 10 11 10 14 14 10 10 11 Sara Bolognesi 31

  32. Resolution calibration hit resolution distribution for each SL hit resolution = vdrift×smeantimer MB2 MB3 MB4 mean 560mm MB1 mean 600mm W2 W2 W1 W2 W2 W1 W1 W2 W1 W1 10 11 14 14 10 10 11 10 10 11 10 10 11 10 deviation from linearity B off (local run) CMS NOTE 2005/018 B = 3.8 T (global run) With B on the resolution become worse because of deviations from linearity Sara Bolognesi 32 half PhD seminar (2008 Febr. 22 Torino)

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