1. The CMS Detector Paoti Chang National Taiwan University
Workshop on LHC Physics and the Strategies for Discovery
Taipei, Taiwan, Jan. 14, 2008
1/14/08 NTU, Taipei
The CMS Detector

2. Detector Requirement
Good Muon identification;good dimuon mass resolution (~1% at 100 GeV); distinguish charge at 1 TeV.
Good momentum resolution for charged tracks. Efficient triggering and off-line tagging on t and b-jets.
Good EM energy resolution; good diphoton and dielectron mass resolution; wide geometrical coverage; p0 rejection and efficient photon and lepton isolation
Good missing-transverse-energy and dijet mass resolution
 high-field solenoid, full-silicon-based inner tracking
system and a homogenous scintillating-crystal-based
electromagnetic calorimeter
1/14/08, NTU, Taipei
The CMS Detector

3. Overview of the CMS Detector
1/14/08, NTU, Taipei
The CMS Detector

4. Superconducting Magnet
Special features:
1. Winding composed of
four layers
2. Mechanically reinforced
with aluminum alloy
3. Large dimension
6.2 m cold bore, 12.5m length,220-t mass
1/14/08, NTU, Taipei
The CMS Detector

5. Main parameters CMS decides to use lower field, 3.8T.
1/14/08, NTU, Taipei
The CMS Detector

6. CMS Barrel Yoke ready for coil and muon Detector
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The CMS Detector

7. Inner Tracking System ⇕
Provide precise measurements of track trajectories and secondary vertices.
L= 1034 cm-2 s-1  1000 particles from >20 inter.
high granularity and fast response of electronics
Keeping minimum amount of material
3 layers of pixel to reduce occupancy ( cm)
10 layers of silicon strip detectors (R ~ 1.1 m)
endcaps: 2 disk pixel and 3 plus 9 strip on each side ⇕
1/14/08, NTU, Taipei
The CMS Detector

8. Overview of the tracker layout
Acceptance |h|<2.5, 200 m2 silicon area, 1440 pixel and strip modules.
pixel: 100x150 mm2; Inner silicon: 10cm x 80mm; outer silicon: 25cm x 180 mm
1/14/08, NTU, Taipei
The CMS Detector

9. Expected Hadron Fluence and Radiation Dose
L = 500 fb-1, 10 years of LHC running
Surface damage on readout chips  0.25mm CMOS chip (rad. hard)
Increasing leakage current  low temperature -10C to -27C
transient phenomena
1/14/08, NTU, Taipei
The CMS Detector

10. Pixel Detector barrel support structure Layout overview 
material budget
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The CMS Detector

11. Barrel Pixel Detector Modules
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The CMS Detector

12. Forward Pixel Sketches of two types of FPix panels
Half cylinders
Sketch of of a plaquette mounted in a panel
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The CMS Detector

13. Status of Pixels
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The CMS Detector

14. Overview of Silicon Strip Detector
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The CMS Detector

15. Silicon sensor 320 mm sensors 500 mm sensors Active region
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The CMS Detector

16. Silicon Tracker Inner Barrel and Endcap
Exploded views of a module of two sensors
Three TIB modules in a shell
1/14/08, NTU, Taipei
The CMS Detector

17. Outer Silicon Tracker
Each sector consists of 9 front petals and 9 back petals
d = 2.3 m
Endcap outer silicon strip detectors
TOB wheel
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The CMS Detector

18. Rod an Petal Double sided rod Front and back panels for TEC
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The CMS Detector

19. Expected Performance Transverse momentum Impact parameter in r
Impact parameter in z
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The CMS Detector

20. Electromagnetic Calorimeter
The CMS ECAL consists of a hermetic homogenous calorimeter made of 61200
lead tungstate (PbWO4) crystals in the central barrel part, ~7324 crystals in each of the two endcaps, and a preshower detector in front of the endcap crystals.
Advantages of PbWO4:
1. high density (8.28 g/cm3); 2. shorter rad. Length (.89 cm)
3. short Moliere radius (2.2 cm);
4. fast radiation decay time (80% of the light in 25 ns)
 fine granularity, radiation hardness and compact calor.
1/14/08, NTU, Taipei
The CMS Detector

21. CMS-PbWO4
1/14/08, NTU, Taipei
The CMS Detector

22. Layout of the CMS ECAL Barrel: |h| < 1.479 360 fold in f
2x85 fold in h
crystal size:
front: 22x22 mm2
back: 26x26 mm2
length: 230 mm
25.8 X0
Endcap:
1.479< |h| < 3.0
1 unit = 5x5 crystals.
crystal size:
front: 28.62x28.62mm2
back: 30x30 mm2
length: 220 mm
24.7 X0
1/14/08, NTU, Taipei
The CMS Detector

23. ECAL Modules Barrel supermodule (1700 crystals) Module of 200 crystals
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The CMS Detector

24. ECAL-Barrel
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The CMS Detector

25. Preshower Detector 1.653<|h|<2.6; total length 20 cm.
Twp parts: lead radiators and silicon strip sensors.
Taiwan involvement:
NCU: 1/4 silicon
sensors
NTU: System
Motherboards
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The CMS Detector

26. Calibration and Resolution
channel-to-channel variation:
use lab. measurements on light yields and photo-dio. response.  5% in barrel and 10% in endcap
Beam test
p0/h →gg in data; w →en.
Laser Monitor system
Energy resolution
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The CMS Detector

27. Performance of a typical 3x3 crystals
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The CMS Detector

28. Status of ECAL Endcaps & Preshower
Preshower: testing micro modules, motherboards and
preparing to install in April
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The CMS Detector

29. Longitudinal View of the CMS Det.
HCAL Barrel
HCAL Endcap
HCAL Forward
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The CMS Detector

30. HCAL Barrel (HB)
The HB consists of two half-barrels, each of which contains 18 wedges. Each wedge corresponds to 4 f sectors.
The absorber consists of a 40-mm thick front steel plate,
mm-thick brass plates,
mm-thick
brass plate, and
a 75-mm-thick
steel back
plate.
16 h
5.82 lI at 90 and 10.6 lI at h=1.3
wedge
Half barrel
1/14/08, NTU, Taipei
The CMS Detector

31. The HCAL Tower Segmentation
Plastic scintillators
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The CMS Detector

32. Endcap Calorimeter (HE)
Yoke
Close to magnet, non-conducting absorber has to be used. 
C26000 cartridge brass
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The CMS Detector

33. HCAL Endcaps Scintillator Tray HE Wedges 1/14/08, NTU, Taipei
The CMS Detector

34. Forward Calorimeter Situate at |h| = 5
Detect particles through its Cherenkov light.
Require good EM response (electrons).
Serve as luminosity monitor
Methods: zero counting and average ET per tower
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The CMS Detector

35. Expected Performance Jet energy resolution 1/14/08, NTU, Taipei
The CMS Detector

36. Muon System Identify muons, measure momentum and trigger muon events.
The muon system consists of three types of gaseous detectors:
1. four layers of drift tubes in |h|<1.2
2. cathode strip chamber covering |h| to 2.4
3. resistive plate chambers
6 layers in barrel and 3 in endcaps ( |h| < 1.6 )
1/14/08, NTU, Taipei
The CMS Detector

37. Layout of Drift Tube Chambers
One layer is inside the yoke, one is outside, and the other two are embedded within the york.
One of the five wheels.
60 chambers in the first three layers and 70 in the last.
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The CMS Detector

38. Sketch of Drift-Tube Cell
Gas:
85% Ar + 15% CO2
Top and bottom plates are grounded. The voltages applied to the electrode are +320V for wires, V for the strips and V for the cathode.
1/14/08, NTU, Taipei
The CMS Detector

39. Installation of MB1 on Wheel 2
Each DT chamber is made of 3 (or 2) superlayers, each of which is made of 4 layers of rectangular drift cells.
1/14/08, NTU, Taipei
The CMS Detector

40. Quarter view of the CMS Detector
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The CMS Detector

41. Layout of a CSC & a Schematic View of a Single Gap
HV: kV
7 trapezoidal panels forming a 6 gas gaps.
Gas:
40% Ar + 50% CO2 + 10% CF4
1/14/08, NTU, Taipei
The CMS Detector

42. Resistive Plate Chamber
Advantage: tagging the ionizing time much shorter than 25ms  good for triggers
Gas:
96.2% C2H2F % C2H % SF6
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The CMS Detector

43. Schematic Layout for Barrel RPC
r-f view
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The CMS Detector

44. Layout for Endcap RPC
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The CMS Detector

45. Expected Performance
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The CMS Detector

46. Status of the Muon System
DT muons:
a. Install tower electronics b. Test and commission
2. CSC
a. All chambers and electronics are installed B. Do more tests.
1/14/08, NTU, Taipei
The CMS Detector

47. Summary
After so many year hardwork, majority of the detector and electronics are installed and commissioned.
Problems and difficulties are foreseen before collisions.
Tight schedule for Endcap ECAL and Preshower.
Keep testing and looking forward to LHC physics.
1/14/08, NTU, Taipei
The CMS Detector