1. CMS muon detectors and muon system performance
Physics goals
Muon system layout
Barrel Drift Tubes Chambers (DT)
Endcap Cathode Strip Chambers (CSC)
Resistive Plate Chambers (RPC)
Muon system performance
Ezio Torassa – Sez. INFN di Padova
LHC days in SPLIT – SPLIT (Croatia) – October 4-7 th 2000
E. Torassa

2. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Physics goals
The 4 lepton channel is crucial for the discovery of the SM Higgs boson
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

3. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Physics goals
H g Z Z(*) g 4 m SM Higgs
(mass resol. ~ 1 GeV)
h, H, A g m+ m SUSY Higgs
q , g g multi-lepton + multi-jet + Etmiss Superpartners
(muon recognition in multi-jet environment)
Z’ g m+ m New Gauge Bosons
(Pt m measur. and sign determ. Above 1TeV)
etc … ~ ~
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

4. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Muon system layout
E. Torassa
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

5. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Muon system layout
Barrel (h<1.3)
DT - RPC
particle rates < 10 Hz/cm2
low B field < 0.8 T
Endcap ( 0.9<h<2.4)
CSC - RPC
particle rates Hz/cm2
high B field up to 3 T
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

6. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Muon system layout
DT goals
Measure f and z points along muons track segements
in the barrel region to:
identify muons and measure charge and momentum
identify the bunch crossing associated to every muon track
CSC goals
Like DT but in endcap regions
RPC goals
Measure f points along muons track segements in the barrel and endcap regions to:
identify muons and assign a bunch crossing to the tracks
estimate their pt
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

7. Barrel Drift Tubes Chambers
Anode ch.
Superlayer
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

8. Barrel Drift Tubes Chambers
Cell designed to have electric field as uniform as possible ò
Drift velocity mm/ns
Gas mixture Ar/CO2 ( 85/15 % )
Vc / Vs / Vw = -1.2/+1.8/+3.6 (kV) ò
E = kV/cm
Electric field kV/cm
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

9. Barrel Drift Tubes Chambers
DT performance
Results from July 1999 CERN-H2 test beam
The prototype is a narrow MB2 type superlayer with the final cell design
Single cell s ~ 170 mm
Single cell efficiency ~ 99.8 %
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

10. Barrel Drift Tubes Chambers
DT performance in magnetic field Bz
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

11. Barrel Drift Tubes Chambers
DT trigger
BTI front-end device
TRACO device
Bunch and Track Identifiers:
Synchronous device with 80 MHz FIFO unit, it stores times with 12.5 ns resolution
Track Correlator
TMEAN = T MAX is independent to the angle and the position of tracks
Output: x, y, TRGLEVEL
Output: X, Y, CORR/TRGLEVEL
The clock count identify the bunch crossing
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

12. Endcap Cathode Strip Chambers
4 disks
2-3 rings (3 for ME1)
~ 2.5 million wires
Anode ch.
Cathode ch.
(*)(ME4 staged)
Chamber Trapezoidal shape
covers 10o or 20o sectors
Each Chamber has 6 gas gap planes
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

13. Endcap Cathode Strip Chambers
CSC gas gap plane is a multiwire proportional chamber
H.V. wires 3.6 kV (Qcath. ~ 110 fC, Qanode ~ 140 fC)
3.2 mm
9.5 mm
Wires measure r-coordinate
Wires spaced by 3.2 mm ganged in groups of 5-16
Wires group width mm (digital readout)
Strips run radially to measure f coordinate mm
Strips width mm (analog readout)
Gas mixture Ar/CO2/CF4 ( 40/50/10 % )
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

14. Endcap Cathode Strip Chambers
CSC performance
Strips
Single layer efficiency ~ 100 %
Single layer resolution ~ 50 mm
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

15. Endcap Cathode Strip Chambers
CSC performance in magnetic field
Br < 1 T
|f| < 6o
s < 150 mm
s ~ 60 mm
Bz < 3 T
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

16. Endcap Cathode Strip Chambers
CSC trigger
Comparator device
Cathode Local Charged Track Processor
thresh
Latch
Latch
Position
Angle
Bunch crossing ident. ò
4 comparators
localize hits to within a half-strip
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

17. Resistive Plate Chambers
RPC MB
RPC ME
360 Stations
252 Stations
(6 shells , 12 sectors)
(4 disks , 1 or 3 rings)
80640 strips
92162 strips
FEB
ME2
Strip orientation
MB2
MB1, MB3, MB4
Strip orientation
30o
AL bars
Each station has 2-3 double-gap modules
Chamber Trapezoidal shape covers 10o or 30o sectors
RPC ME2 station has 6 double-gap modules
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

18. Resistive Plate Chambers
RPC double gap module
Avalanche created inside the gap, charge induced on strips
Electrode resistivity ò
Rate capability ò
Gap width
Time performance
Avalanche operation mode
(higher rates w.r.t. streamer mode)
Operating H.V kV
Gap width mm
Bakelite bulk resistivity W cm
Bakelite thickness mm
strip width ~ 35 mm
Gas 95% C2H2F4 , 5% i-C4 H10
Double gap improves
efficiency and time resolution
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

19. Resistive Plate Chambers
RPC performance
Trigger efficiency
Trigger efficiency
s < 3 ns
Efficiency ~ 100 %
RPC time resolution (ns)
RPC efficiency
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

20. Resistive Plate Chambers
RPC trigger
Pattern comparator trigger device
Because of energy loss fluctuations and multiple scattering there are many possible patterns in RPC chambers for similar muons
The PACT electronic performs two functions:
requires time coincidence in 3 or 4 stations
compares hits to predefined patterns for muons of various
momentum (obtained from simulation)
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

21. Muon system performance
Muon Identification
Precision dpt/pt for pt<100 GeV
Charge assignment correct to 99% confidence
Unambiguous bunch crossing identification
Requirements
Muon system with inner tracker
dpt/pt ~ 1 %
Muon system with vertex constraint
dpt/pt ~ 10 %
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

22. Muon system performance
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

23. Muon system performance
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

24. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Conclusions
Madrid MB2: glue on top of 1st layer of I-bemas
Legnaro table for MB3 q SL
FNAL CSC wire winding station
FNAL CSC assembling station
Ezio Torassa LHC days in SPLIT October 4-7 th 2000

25. Ezio Torassa - LHC days in SPLIT - October 4-7 th 2000
Conclusions
CMS muon system is designed to achieve
the LHC physics goals
Required performances were obtained with
tests of detector prototypes
Mass production of chambers has begun
Ezio Torassa LHC days in SPLIT October 4-7 th 2000