Operation of the CMS Tracker at the Large Hadron Collider Thomas Bergauer (HEPHY Vienna) ÖPG/FAKT Annual Meeting Salzburg 9. September 2010

CMS: Compact Muon Solenoid Supraconducting Magnet (4 T) Hadronic Calorimeter Electromagnetic SiTracker (Pixel and Strips) Muon System Magnet Return Yoke Very Forward Weight: 12.500 t Diameter: 15 Length: 21.5 m 9. September 2010 Thomas Bergauer (HEPHY Vienna)

CMS Silicon Strip Tracker Largest silicon tracker built Active area of 198 m2 5.4 m long, 2.4 m diameter Components: Pixel detector (not covered in this talk) TIB (Inner barrel): 4 layers TID: 3 Inner Disks TOB: (Outer Barrel): 6 layers TEC (Endcaps): 9 disks on each side Key features: 9.6 Million readout channels Analog readout Barrel (BPIX) Endcap (FPIX) L ~ 90 cm rmin = 4.4 cm rmax = 10.2 cm 9. September 2010 Thomas Bergauer (HEPHY Vienna)

CMS Tracker in pictures 9. September 2010 Thomas Bergauer (HEPHY Vienna)

CMS Tracker Installation December 2007 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Angular coverage down to 9 degree to the beam-pipe (|η|<2.5) 4 layers and 3 rings contain stereo modules for 2D hit reconstruction Basic Building Block: Detector module 15 148 pieces in total 15 different geometries Modules consist of Carbon fiber/graphite frame Front-end hybrid with APV25 readout chips One or two p-on-n silicon sensor(s), 320/500 micron thick 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Readout Chain 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Commissioning Procedures Analog readout Digitization is done only in off-detector electronics (FEDs) Thus, detector needs to Time-align internally (different cable lengths) Tune laser gain (analog opto-hybrids) Optimize chip parameters (baseline,…) Determine noise and pedestals (zero-suppressed data) Benefit of analog readout Higher position resolution Makes debugging easy 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Operational fraction of SST 98.1% of channels in operation TIB/TID: 96.3 % One ring lost (short, appeared with B field), ~1% HV missing and HV shorts, ~2.5% TOB: 98.8 % One ring lost (short, comes/goes with B field) TEC: 99.0 % One HV PG missing (short) One LV PG missing (short) TID+ TEC+ TOB TIB TID- TEC- 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Signal-to-Noise Ratios Charge clusters of associated tracks Divided by noise determined during calibration (pedestal) run Non-perpendicular tracks normalized by trigonometry Landau convoluted with Gaussian MP value taken for summary TIB TID TOB TEC thin TEC thick 19.4 18.5 22.5 19.1 23.4 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Tracker Alignment p>3 GeV/c pT>0.65GeV/c Only modules with >200 hits 15148+1440 sensors 6 degree of freedom each O(10mm) accuracy Minimization hit/track residuals c2 Two approaches: Millipede (II): Global minimization “Hits and Impact Points” (HIP): local minimization of sensor position, iterative, detailed track model Kalman Filter-based fit method working on “correlated” elements, iterative Applied sequentially from large substructures to sensor level Distributions of Mean Residual (DMR): median of the residual distributions in each sensor 2010 cosmics and collision events used for present alignment: 1.5M cosmic tracks (p>4 GeV) 1.7M collision tracks (p>3 GeV) with constraint to primary vertex 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Summary CMS Tracker (together with whole CMS experiment) performs excellently in both cosmics and pp collision runs 98,1 % channels in operation Tracker uses analog readout from detector to off-detector electronics Makes different calibration runs necessary Signal-to-noise ratio meets expectations Alignment algorithms reveal accuracy of 10μm Tracker contributes to the high quality physics data CMS delivers 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Thank you for your attention THE END 9. September 2010 Thomas Bergauer (HEPHY Vienna)

APV25 Peak vs. Deconvolution mode output charge for each strip represents a weighted sum of three consecutive pipeline cells designed to avoid signal pile-up in high luminosity operations necessary whenever bunch separation is less than a few hundred nanoseconds 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Collected Events Cosmics muons 2008: 3M tracks in tracker 2009: 4M tracks 2010: 2.2M tracks ~ 4% in pixel detector volume alignment, calibration, noise, resolution pp Collisions Dec 2009 (900GeV+2.36 TeV): ~300k MinBias Events 2010 (7 TeV): ~3000 nb-1 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Track Reconstruction Efficency Tracks reconstructed in three steps: seeding: hit triplets (mainly pixel hits) or pairs + beam spot used as track candidate Pattern recognition: track candidate propagation (Kalman filter), addition of new compatible measurements, track candidate cleaning Final Track Fit: track parameter estimator Track Selection: fakes rejected with quality cuts Iterated several times: hits associated to reconstructed tracks are removed different seeding algorithms different quality cuts 9. September 2010 Thomas Bergauer (HEPHY Vienna)

Thomas Bergauer (HEPHY Vienna) Impact parameter transverse longitudinal 9. September 2010 Thomas Bergauer (HEPHY Vienna)