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. 93% lumi livetime during stable beam:
How are we doing
93% lumi livetime during 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
L=1027Hz/cm2
L=1028Hz/cm2
L=1029Hz/cm2
L=1030Hz/cm2
L=3 1030Hz/cm2
L= 1031Hz/cm2
L= Hz/cm2
Today

4. Trackers and tracking

5. Tracker material
MC now
TDR

6. and it seems correct Nuclear Interactions Conversions Conversions

7. Analitical fit reproduces measurement to 0.01%
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. Low P J/Ψ Single track pt resolution extracted from J/Ψ width
TDR: almost mission accomplished for low P
J/Ψ
Y(1,2,3S)

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

10. High P (cosmics) ~8% for pt=500 GeV
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. Probes passing the matching Probes failing the matching
Tracking efficiency
Probes passing the matching
Probes failing the matching
J/Psi Tag and probe
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 pT about 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. HLT 15 GeV g efficiency vs Supercluster energy reconstructed
ECAL trigger
HLT 15 GeV g efficiency vs Supercluster 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 point is crystal intercalibration :only 25% have been exposed to e beam

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

21. in the barrel the scale is now set by the π0 calibration
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. Down to pt=20 GeV and 5% Jet Energy Scale
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. qT distribution of g-jet candidates
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 comparison for b-tagging observables
DATA/MC ratio is close to 1 for all observables

31. Trigger requirements Online requirement In early phases: keep L1 rate
Collision rate MHz
Event size Mbyte
Level 1 Trigger Input 40 MHz
HLT trigger input KHz
Mass storage rate 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 :

35. Backup slides

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

37. Tracker De/Dx

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

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
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
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. Missing Et
And pileup seems
to be under control

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. JES: dijet pt balance Calo-jets Calo-jets JPT-jets JPT-jets
P-flow-jets
after relative response correction
(shown is error band of 2%⋅η adopted in
physics analyses
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)