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LHC Physics Commissioning - part 1 -

LHC 2006 Martignano, 12-18 June 2006. LHC Physics Commissioning - part 1 -. Roberto Tenchini INFN - Pisa. Credits to: Roger Bailey, Tommaso Boccali, Fabiola Gianotti, Dan Green, Fabrizio Palla, Gigi Rolandi. Experiments at the LHC. CMS. Aleph. LEP. -. LHC. Opal. A LICE. L3.

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LHC Physics Commissioning - part 1 -

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  1. LHC 2006 Martignano, 12-18 June 2006 LHC Physics Commissioning- part 1 - Roberto Tenchini INFN - Pisa Credits to: Roger Bailey, Tommaso Boccali, Fabiola Gianotti, Dan Green, Fabrizio Palla, Gigi Rolandi

  2. ExperimentsattheLHC CMS Aleph LEP - LHC Opal ALICE L3 • 2007 Pilot Run • 2008 1-10 fb-1 • 2010 100 fb-1 SPS Delphi ATLAS PS LHCb Experiments at LHC: ATLAS A Toroidal LHC ApparatuS(proton-proton collisions) CMS Compact Muon Solenoid (proton-proton collisions) ALICE A Large Ion Collider Experiment (Ion-ion collisions) LHCb (Study of CP violation in B-meson)

  3. LHC cross sections and rates • At Highest Design Luminosity (1034 cm-2 s-1) • SM Higgs (115 GeV/c2): 0.1 Hz • t t production: 10 Hz • W l n: 102 Hz • bb production:  106 Hz • Inelastic: 109 Hz • Beam crossing every 25 ns • 25 pileup event / beam crossing at High Lumi Selective triggers are required These rates will be achieved after a long period of commissioning & operation In parallel well understood detectors must be operational to exploit the rich physics

  4. Muon spectrometer Hadronic Tile Calorimeter Solenoid 22 m Toroid Inner Detector Electromagnetic Calorimeter 44 m Weight ~ 7000tons

  5. Total weight : 12,500 t Overall diameter : 15 m Overall length : 21.6 m Magnetic field : 4 Tesla TheCompactMuonSolenoid (CMS) CALORIMETERS SUPERCONDUCTING ECAL Scintillating PbWO4 HCAL Plastic scintillator COIL Crystals brass sandwich IRON YOKE TRACKERs MUON ENDCAPS MUON BARREL Silicon Microstrips Pixels Resistive Plate Cathode Strip Chambers (CSC) Drift Tube Resistive Plate Chambers (RPC) Chambers (RPC) Chambers (DT)

  6. ATLAS

  7. CMS

  8. LHC Startup Schedule Expt’s CLOSED Recent news: Delay of two months On this schedule Experiments are closed on 31st of August

  9. Physics Commissioning: two main phases • Before data taking starts: • Understand and calibrate the detectors with test beams, cosmics, surveys, B-field measurements, etc. • Prepare software tools: simulation, reconstruction, calibration and alignment procedures • With the initial LHC data: • Commission and calibrate in situ detector and trigger with physics samples • Understand Standard Model physics at 14 TeV • Measure background to New Physics Prepare the road to discoveries

  10. Geant4 simulation of test-beam set-up y x z The Atlas combined test beam O(1%) of ATLAS Beam: electrons, muons, pions, Photons of various Energies With B- field All ATLAS sub-detectors (and LVL1 trigger) integrated and run together with common DAQ and monitoring, “final” electronics, slow-control, etc. Gained lot of global operation experience during ~ 6 month run.

  11. ATLAS test beam: Momentum reconstruction, 9 GeV pion data, B=1.4 T

  12. Sagitta resolution vs momentum Barrel Data fitted with: 2 2 K ( K / P ) s = + meas 1 2 meas K intrinsic resolution term; K multiple scattering 1 2 ATLAS preliminary Pmeas from beam magnet From the fit (36 mV) Data Simulation K1 = 51±3mmK1 = 40±3 mm x/X0~ 0.27±0.04x/X0~0.32 ±0.03 50 mm accuracy achieved at high muon momentum (corresponds to /p ~ 10% at 1 TeV) mm

  13. ATLAS Test beam : Combined calorimetry: data/simulation comparison for pion response in LAR EM + Tilecal Understanding jets requires significant input from simulation: Check simulation with test beam pions.

  14. Primary electron ID track extrapolated to ECAL and compared to calo cluster Converted photon  track  cluster Matching tracks to clusters ATLAS preliminary ATLAS @ LHC: -conversion probability is  30%  important to develop (and validate !) efficient reconstruction tools Work in progress to reconstruct full   e+e- in ID

  15. CMS: Magnet Test/Cosmic challenge in SX5 Check closure tolerances, movement under field and muon alignment system (endcap + barrel + link to Tracker). Check installation & cabling of : ECAL/HCAL/Tracker[dummy] inside coil, including cabling test. Establish stable operation of coil, cryo, power supply and control system. Map the magnetic field. Check field tolerance of components within and outside the yoke Test individual and combined operation of subdetectors in ~20o sector of CMS with magnet & central DAQ.Record cosmics. Try out 24/7 operation of CMS. = "cosmic challenge" CMS closed for magnet test in SX5 surface building: winter 05-06

  16. B-field Mapping Ramp down to 4.2K ~ 1 month, then 2 months commissioning and 1.5 months of B-field mapping To achieve 1% Pt resolution at 100 GeV DB/B~0.1%-0.5% (tracker volume) (about 1% uniform for construction) DB/B~0.4% calorimeters DB/B~1% muon chambers How: Hall probes + NMR Commissioning theCMS Magnet

  17. CMS MTCC Overview • End of May: CMS closed • Commission magnet • Sub-detectors brought up in separate then combined operation • Alignment system commissioning • A few days of steady magnetic field at end • Mid July: reopen + end • Remove Tracker tube, complete fieldmapper installation/survey • Close up • End of July: Field mapping through August (Muon and HCAL can continue testing) • September, lower… Probable mapping points 0, 1 (for HI), 2, 3.5,4 Tesla? (Each twice once going up and once coming down for hysteresis

  18. Magnet test: cosmic challenge:barrel DT’s in sector 10 of YB+2, YB+1 and CSC’s of YE+1 lower 60 deg sector provide the principal triggers. TK dummy tube with alignment disk & cables HB+ active sectors TK (elements in dummy tube to be defined) EB supermodules 11 10

  19. Physics Tools Commissioning • Achieve design performance for selection and reconstruction of (esempi da CMS): • High pT Muons • Primary and Secondary verteces • High ET photons - electrons • Jet, Missing ET Operations : Before Pilot Run During Pilot Run Low lumi Physics First 108 Trigger First run at 2X1033

  20. Riding a muon in CMS !

  21. In surface: data taking in self triggering mode to map noisychannels and first synchronization. In the pit : commissioning as soon as cooling is trhere; timing for LVL1 trigger Muon System. Example: DT

  22. Muon System. Example: DT (Drift Tubes) • Fine time synchronization before beam injection in LHC for relative t0 . • Global t0 measured from inclusive muons • Measurement of drift velocity (with a few hundreds of events is measured at 0.2%)

  23. Alignment: intrinsic resolutions are of the order of 200um The target is reaching an alignment of 100-500 um among muon stations and with the Tracker Optical system : rigid structures + optycal links (laser, CCD) Relative position of chambers known ~ 150 um The system requires validation with the magnet : Bon/Boff generates shifts ~ cm Muon System : Alignment

  24. Muon System alignment using real tracks ( ) • 790 chambers, 6 parameters per chamber • One day at low luminosity is enough to show misalignment of the order of one fourth of mrad

  25. Absolute pT scale checked with

  26. Muons : add the Tracker Resolution on 1/pT adding the Tracker Resolution on 1/pT with Muon System + vertex constraint

  27. Tracker Alignment Silicon Strip Tracker • More than 15000 modules to align, O(105) parameters • Opthical link between Muon System and SST • Pixels added after Pilot Run • three cylindrical barrel layers at • 4.4 cm, 7.5 cm and 10.2 cm • two pairs of end-cap disks at • |z| = 34.5 cm and 46.5 cm up t Pixels

  28. Tracker Alignment • Strategy • Initial alignment from survey + opthical link precision O(100 mm) • Alignment with tracks O(10 mm) • Pattern recognition possible even with misalignment of 1 mm The systematic error is added to the pattern recognition, thanks to the high granularity the fake-rate is under control • Studies with LHC tracks : • minimum bias for the pixel • Semileptonic W’s for muon ch. and SST

  29. Tracker Alignment • Algorithms for O(105) parameters being developed • Full Matrix invertion (Millipede) • Iterative algorithm leading to block of 6NX6N matrices (Hits and Impact Point method) Example for the Pixels

  30. Misalignments scenarios: 100 pb-1 and a few fb-1

  31. Estimates for 100 pb-1 and a few fb-1 Perfect alignment: resol. ~3 % Short-term 100 pb-1: resol. ~6 % curve reproduces tracker misalignment Long term a few fb-1: degraded by factor 1.4 wrt. perfect alignment

  32. Estimates for 100 pb-1 and a few fb-1 pT resolution integrated in h Z peak visible even with the first rough alignments

  33. Primary vertex • Beam spot measured with data, the two beams are not colliding in the geometrical center of CMS • Plot with minimum bias 500 events only : uncertainty of 8 microns in the transverse plane y d0=L sin (a-f) f L a d0 x

  34. Primary vertex in z and pile-up Histogram method: pT weighted tracks Longitudinal impact parameter with 3 pixel hits VERY FAST: Timing (2.8 GHz, PIV, qq100@1034, global region) 130 ms (triplet) + 7 ms (fitting+vertexing) Efficiency ~ 100% Purity >~80% Effect of tracker misalignment on primary vertex reconstruction is weak.

  35. transverse impact parameter resolution Secondary Vertexes Impact parameter resolution in different conditions Quality of secondary vertexes In different misalignment scenarios

  36. 76000 PW04 crystals inter-calibrated at the 0.5% level ! Benchmark channel Electrons and Photons • Calibration strategy • All crystals precalibrated with 60Co source (1 MeV gammas) • A few supermodules precalibrated with electron beam (20 e 250 GeV) • The rest using cosmics, with increased APD gain • Calibration during LHC data taking with electrons • A laser system is monitoring the time-dependent calibration

  37. Electrons and Photons : before Pilot Run Demonstrated with a supermodule on test beam that the change of transparency of a crystal because of radiation is followed by the laser monitoring system. Calibration with cosmics vs test beam

  38. Electrons and photons: initial intercalibration with jets • The azimuthal simmetry can be exploited for a first intercalibration with inclusive jets

  39. different regions in η Electrons and photons: calibration with tracks Important to select tracks with low bremsstrahlung 5 fb-1

  40. Jets and Missing ET • HCAL Calibration • Megatile scanner: a collimated 60Co gamma source • Measure relative yield to 1% during costruction • Moving wire source: • Continuous monitoring to 1% level • Test beam also with Magnetic Field • Durante LHC run: light injection (UV and blue): • Used for timing and linearity

  41. Jet e Missing ET • Combined ECAL – HCAL beam tests

  42. Monte Carlo calibration of jets Jet Corrections Given a jet clustering algorithm Experimentally reconstructed jet Monte Carlo jet Partons

  43. Jet calibrations from LHC data • Examples • g/Z+jet • W-> jj

  44. Missing ET calibration from data • Example • semileptonic ttbar From ATLAS. Iterate to avoid calibrating on SUSY !! top mass peak vs sidebands

  45. Trigger and DAQ • Level 1 triggerbased onmuon & calorimeters , • then High Level trigger using reconstruction algorithms L1 trigger 40 MHz 100 kHz High Level Trigger (computer farm) Yes/No CMS 3.2 ms buffer 1 s buffer 100 Hz 1 MB/event Off-line analysis

  46. Level-1 Trigger

  47. 3D-EVB: scalable DAQ Data to surface: Average event size 1 Mbyte No. FED s-link64 ports > 512 DAQ links (2.5 Gb/s) 512+512 Event fragment size 2 kB FED builders (8x8) ≈ 64+64 DAQ unit (1/8th full system): Lv-1 max. trigger rate 12.5 kHz RU Builder (64x64) .125 Tbit/s Event fragment size 16 kB RU/BU systems 64 Event filter power ≈ .5 TFlop DAQ Scaling&Staging

  48. HLT Trigger tables

  49. DAQ 05-07: milestones • Dec 2004 Pre-series: installed DAQ integration started • Jan 2004 Data to Surface (D2S): Production&Procurement started • Apr 2005 Online software: DAQkit 3.0 released • XDAQ 3, RC2, FF, DCS, DB, for 904 and Cosmic Challenge • Nov 2005 D2S: end of production, start of installation in USC • Jan 2006 FRL-FED readout and DCS commissioning • Feb 2006 Cosmic challenge • Oct 2006 Start of Trigger&DAQ commissioning • Central Trigger & DAQ integration, DBs and Connection with remote data storage • Multiple Readout Builders and multiple TTC/DAQ Partitions • DAQ Slices and Farms PC procurement for first run • Jun 2007 Ready for first collisions

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