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CMS status

CMS status. A walk through the performance of CMS at LHC Will try to avoid overlap with later presentations on physics performance Acknowledgements: the material presented here is the result of work of > thousand people who have built, commissioned CMS over the years and to those who have

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CMS status

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  1. CMS status • A walk through the performance of CMS at LHC • Will try to avoid overlap with later presentations on physics performance • Acknowledgements: the material presented here is • the result of work of > thousand people who have • built, commissioned CMS over the years and to those who have • analyzed the data which has been pouring in the last months: to them goes • the merit of the results shown, mine are only the mistakes/omissions • T. Camporesi , CERN

  2. CMS

  3. L= 5 1031Hz/cm2 L= 1031Hz/cm2 L=3 1030Hz/cm2 L=1030Hz/cm2 L=1029Hz/cm2 L=1028Hz/cm2 L=1027Hz/cm2 How are we doing 93% lumilivetimeduring stable beam: Most losses due to study beam related issues with readout: fixed since end of August Running with L1 trigger rate between 45 and 70 KHz (sustained peaks at 90 KHz) and logging rate between 350 and 600 Hz Today

  4. Trackers and tracking

  5. Tracker material MC now TDR

  6. and it seems correct Nuclear Interactions Conversions Conversions Conversions

  7. Magnet • In order to achieve P resolution goals the magnetic field has to be understood to the permill level Analitical fit reproduces measurement to 0.01%

  8. J/Ψ TDR: almost mission accomplished for low P Low P Single track pt resolution extracted from J/Ψ width Y(1,2,3S)

  9. Intermediate P No bias with a precision of 0.15% W→mn Z→mm

  10. Split cosmic track at point of closest approach to ‘IP’ High P (cosmics) Tag-leg Estimate momentum scale bias by assuming no infinite P tracks Probe-leg ~8% for pt=500 GeV -0.044±0.022 TeV-1

  11. Vertex and IP resolution Alignment: cosmics and early data I.P. Pixel Vertex resolution Silicon Tracker Z X

  12. Tracking efficiency J/Psi Tag and probe Probes failing the matching Probes passing the matching and it is not affected by pileup

  13. Muons

  14. Muon trigger J/Ψ ms Tag&probe barrell transition endcap

  15. Performance “Soft muon”: a tracker track matched to at least one CSC or DT stub, to collect muons down to pTabout 500 MeV in the endcaps (e.g. for J/Ψ) “Tight muon”: a good quality track from a combined fit of the hits in the tracker and muon system, requiring signal in at least two muon stations to improve purity. J/Ψ ms Tag&probe J/Ψ ms Tag&probe

  16. μ charge id • Cosmics ( track split and two halves compared) Mis-ID ~1%

  17. Electrons,g and ECAL

  18. ECAL trigger HLT 15 GeVgefficiency vsSupercluster energy reconstructed L1 5 GeV threshold Barrell (50%) 5.6 GeV Endcap (50%)6.7 GeV L1 8 GeV threshold Barrell (50%) 8.9 GeV Endcap (50%) 10.8 GeV

  19. ECAL TDR small constant term needed to detect narrow γγ resonances and test beam exposure ( 25% of detector) confirmed the potential of the PbWO crystals but key pointis crystal intercalibration :only 25% have been exposed to e beam

  20. p0 combined with splashes and fsymm Reaches 0.5 to 1.2 % depending on h in barrel comparison with e-beam calibrated crystals ECAL calibration:π0 Online π0 streams p0,splashes, f-symm 250 nb-1 p0 250 nb-1

  21. ECAL energy scale in the barrel the scale is now set by the π0 calibration EB ~ 1% ….. EE ~ 3%

  22. HCAL & Jets

  23. HLT efficiencies: calo Jets: just data i.e. use μ-triggered events and check turn-on curves on reco jets without any energy corr. HLT Trigger : E> 15GeV Trigger : L1 E> 6GeV Just data l Barrel HLT Trigger : E> 15GeV Trigger : L1 E> 6GeV JES corrected Endcap

  24. isolated part response

  25. Particle flow jets Down to pt=20 GeV and 5% Jet Energy Scale

  26. Jet Triggered Charged particle Spectra Using Jet trigger it is possible to extend the momentum range of charged particle spectra Cross sections scaled empirically by (√s)5.1

  27. Missing Et

  28. Events with isolated g qT distribution of g-jet candidates CALO TC-MET PF-MET Missing recoil energy = Missing Et correction factor (depends on Quark flavor and JES)

  29. b-Tagging

  30. DATA/MC ratio is close to 1 for all observables Data-MC comparison for b-tagging observables

  31. Trigger requirements Online requirement Collision rate 40 MHz Event size 1 Mbyte Level 1 Trigger Input 40 MHz HLT trigger input 100 KHz Mass storage rate 300 Hz System Deadtime ~% Event rate Level-1 input ON-line HLT input Selected events to archive In early phases: keep L1 rate <70KHz (only 50% of Filter farm installed) and use HLT trigger menus adapted to Luminosities to reduce logging rate to <500 Hz OFF-line

  32. trigger • Name of the game: keep trigger as loose as possible: new L1 and HLT menus ~every doubling of lumi ( LHC lumi doubling time has been ~10 days since start of collisions!) Level 1 rates: predicted first from MC and after first fills extrapolated to higher Lumi. Keep unprescaled single physics object threshold compatible with total rate < 70 KHz+ lower threshold multiplicity and isolation triggers

  33. High Level Trigger • With initial luminosities L1 trigger 0-bias or prescaled min-bias + low threshold ‘objects’ (e.g. eγ > 5 GeV, Jets > 10 GeV, loose μ) to keep rate <70 KHz • Adaptive HLT menus in steps of peak lumi: predicted from MC first and then extrapolated from earlier data taking

  34. Conclusions • The goals set out by the CMS founding fathers are close to be met: a feat we did not dreamed to be possible this early in the game • CMS is more ready to produce physics than we ever expected • What will be presented at this workshop are the measure of the quality of the detector and just an appetizer for the future • Last but not least we salute the amazing performance of LHC for (much) more details see : http://cdsweb.cern.ch/collection/CMS%20Physics%20Analysis%20Summaries?ln=en

  35. Backup slides

  36. A figure sums it all Best TOP production candidate secondary vertex 6σ ellipse Top candidate Mass in the 160-220 GeV range

  37. Tracker De/Dx

  38. Trigger & DAQ Event selection ~ µsec latency Trigger Data

  39. Timing with beam Used early fills to do detailed timing scans for calorimeters, CSC, pixel, tracker Optimize delays for data pipelines and trigger primitive generation Good timing essential for background rejection:e.g ECAL

  40. Trigger synchronization Synchronization initially defined from cosmics, beam splashes refined with timing scans Monitored using Zero Bias and/or min bias: Zero bias = trigger on coincidence of beam crossings (L1 trigger =0-bias while # on crossings/orbit was up to 8, ie. L1 rates < 100 KHz

  41. Low P resolution • Use Ks, Φ, J/Ψ to monitor/calibrate vs (η,Pt) J/Ψ Ks Φ Use dE/dX to sel. K Φ

  42. In situ ECAL calib • Use γ from π0 decay and Φ symmetry (assume that integrating over large # of min bias events the energy deposited in crystals at a given pseudorapidity is the same then use test beam pre-calibrated crystals to cross-calibrate various Φ rings) and beam-splashes • For endcaps use beam-splash events form 2008-2009 • Compare with cosmics calibration and electron test beam pre-calibrated crystals to estimate precision • Ultimate calibration will be W en events

  43. Φ symmetry (EB) • 7 TeV data — 7 TeV MC 900 GeV Syst < 0.5% 7 TeV

  44. And pileup seems to be under control Missing Et

  45. Jet Energy scale • Jets are defined using 3 algos: calo only, Calo+ tracks, Particle flow + anti Kt clustering with R = 0.5 • At start use MC to estimate corrections vs (η,pt) • Then use data based methods: dijets pt balance and γ-jet events ( not used YET in physics analyses) Calo-jets Calo+Trk (JPT) ParticleFlow-jets PFJ rely less on ’combined-calo’ 65% Trk, 25% ECAL, 10% HCAL+ECAL Corrects noise and pileup Effect of distribution (vs η) of material and detector structure Corrects pt dependance due to non compensating nature of CMS calorimeters

  46. Calo-jets after relative response correction (shown is error band of 2%⋅η adopted in physics analyses JPT-jets P-flow-jets JES: dijet pt balance 18 <pt<31 GeV 70<pt<120 GeV Calo-jets JPT-jets P-flow-jets The observed trend of higher response in data wrt MC for η>2 is consistent with what is observed in single particle studies

  47. JES: γ + jet • difficulty to define ‘single jet’: use Missing Et Projection Fraction ( MPF) method (used by CDF)

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