# Presentation: 881532

## The ALICEMuon Spectrometer

- Andreas Morsch
- ALICE Collaboration
- IV International Symposium
- on LHC Physics and Detectors
- Fermilab,  May 1-3 2003

## Outline

- Muon Spectrometer overview
- Muon Spectrometer components
- Tracking Chambers
- Trigger Chambers
- Absorbers
- Dipole Magnet
- Expected performance

## Design Goals

- Study the production of J/, ', Y, Y', Y’’  decaying into 
- In the range 2.5 <  < 4 (2° <  < 9°)
- With mass resolutions of 70 MeV at the  J/ and 100 MeV at the Y
- Separate Y  family
- p/p < 1% @ *p* = 150 GeV
- Acceptance at low angles
- Small** **angle** **absorber (beam shield)
- Robust tracking in high random background environment
- High granularity chambers
- Combined angle-angle and sagitta measurement with 3 Tm dipole field

## - 5 stations of high granularity cathode pad tracking chambers (CPCs),  over 1.1 M channels

- - 2 chambers per station

- RPC Trigger
- Chambers

## Front Absorber

- Dipole Magnet

- Trigger

- Tracking Stations

## Tracking

- All stations with cathode segmentation varying with distance to beam axis
- Higher hit density close to the beam-pipe
- Both cathodes segmented (bending/non-bending plane)
- Bending plane resolution <100 m
- Transparent: *X/X*0 ~ 3%
- Muon stations 1-2
- Quadrants
- “Frameless” chambers
- Muon stations 3-5
- Slat design similar for all stations
- Production shared between several labs

## Station 1

- 1999 Prototype
- Anode-cathode gap: 2.5 mm
- Pad size 5 x 7.5 mm2
- Spatial resolution 43 m
- Efficiency 95%
- Gain homogeneity ± 12%

- New requirements (2000)
- Suppression of the Al frames of Stations 1, 2 (+7% acceptance)
- Decrease of the occupancy of Station 1
- Decrease of the pad sizes ( 4.2 x 6.3 mm2)
- Decrease of anode-cathode gap (2.1 mm)

## Station 1

- Mechanical prototype (fall 2001)
- Max. deformation 80 m

- Full quadrant (June 2002)
-  0.7 m2  frameless  structure
- 14000 channels per cathode
- Gas : 80% Ar + 20 % CO2
- 3 zones with different pad sizes

## Test Beam Results

- Unacceptable gain variations
- Solved by:
- Improved closing procedure
- Improved stiffness with central spacer
- Gain variations ±150% → ±20%

- Resolution 65 m

## Stations 3-5

- Tests
- Test-beam Sept. 2002
- Ageing studies at GIF on a small mock-up foreseen by May
- In-beam tests of a rounded shape at SPS planned in June- July
- Production
- Sharing between 4 institutes completed
- Slats production starts Sept. 2003
- Station construction 6/2004-10/2005
- Installation 6/2005-11/2005

## Stations 3-5

- Comparison of different pad sizes:
- 5 x   50 mm2
- 5 x 100 mm2

## FEE: MANU

## FEE: MANU

- MANU with Gassiplex works well
- MANU with MANAS under tests
- MARC3
- Small problems found in last test-beam
- New iteration May 2003
- Final version October 2003

## Trigger

- Principle:
- Transverse momentum cut using correlation of position and angle
- Deflection in dipole + vertex constraint
- 4 RPC planes 6x6 m**2**
- Maximum counting rates
-   3 Hz/cm2 	in Pb-Pb
- 40 Hz/cm2 	in Ar-Ar
- 10 Hz/cm2 	in pp
- important contribution from beam gas
- The chambers
- Single gap RPC, low resistivity bakelite, streamer mode
- Gas mixture: Ar-C2H2F4-C4H10-SF6 @ 50.5-41.3-7.2-1%

## Aging Tests

- Aging test to improve chamber life-time
- Test at the CERN Gamma Irradiation Facility (GIF) show
- Increase of dark current and dark rate
- Chem. surface deterioration (HF)
- Decrease of efficiency
- Bakelite deterioration

## Lifetime Tests

- - Double-layer line-seed oil RPC with dry gas
- - 1% SF6 instead of 4% increases the lifetime
- Constant efficiency over the whole period  (100 LHC PbPb periods)

- 100 PbPb periods equivalent to ~5 year running scenario:
- -  2 years PbPb
- -  1 year Ar-Ar
- -  1 years p-Pb
- -  3 year full intensity pp

## Trigger System: Planning

- Summer 2003 end of test RPC1
- PRR RPC : October 2003
- Production of readout strips : end 2003 (2 months)
- Gas gap production : end 2003 to 02/04
- Beginning of assembling 01/04
- Tests of chambers with cosmics throughout 2004

## Absorbers

- - Suppress /K decay
- - Shield from secondaries in particular at small radii.

## Front Absorber (FA)

- Concrete

- Steel

- Carbon

- Tungsten

- ~10 I (Carbon – Concrete – Steel)
- Design completed
- Stability issues (earth quake)  for support structure to be solved

- FASS

## Small Angle Absorber (SAA)

- Design almost completed after several iterations. Complex integration issues:
- Inner interface
- Vacuum system, bake-out, bellows, flanges
- Outer interface
- Tracking chambers, recesses

- Tungsten

- Lead

- 2°

- 0.8°

## FA and SAA Planning

- Delivery of “big parts” (W, Pb, Fe ...) : all on site in Oct. 03
- Beginning installation FASS : Jan. 2004
- End FASS : Feb. 2004
- Beginning assembling SA1 & SA2 + FA : May 2004
- End of assembling : Sept. 2004
- Installation in Oct. & Nov. 2004

## Dipole Magnet

- Yoke machining : done (Dec. 2002)
- Yoke delivery : April 2003
- Then beginning of installation in testing area
- Dummy coil : done (Oct. 2002)
- Coil winding : started in Jan. 03
- Coils delivery : August 2003
- Then installation for testing
- Power up Oct. 2003
- Moving to final position : March 2004
- End of installation : June 2004

-  3 Tm,  resistive coil
- Bnom = 0.7 T
- Gap l x h x w =
- 5 m x 5.1m x (2.5 – 4.1) m

## Yoke Assembly

## Dummy Coil

## Shaping Tool

## Expected Performance

- J/

- 

- Acceptance down to *p*T = 0

- Geometrical acceptance 5%

## Mass Resolution

- Design values

- Contribution from front absorber higher
- - Non-Gaussian straggling
- - Electrons produced close to muons

- Current value after full simulation and reconstruction:
- 90 MeV (goal < 100 MeV)

## Robustness of tracking

- Hit reconstruction
- Maximum Likelihood - Expectation Maximization algorithm
- Tracking
- Kalman filter

- Reduced dependence on
- background level !

## Muon Cocktail

## Mass – Spectra

- M =90 MeV/c2     at the 
-  Separation of , ’, “
-  Total efficiency  ~ 75%
-  Expected statistics (significance @1yr):
-          central    min. bias
- J/        310          574
-   ’           12            23
-               39            69
-    ‘          19            35
-    “         12            22
- From min. bias events:
- ~ 8k  and ~700k J/ /yr

## Heavy Flavor Production

- Di-muons from beauty production can be used for normalisation.

## Conclusions

- ALICE Dimuon Spectrometer project is overall in good shape
- Some improvement and studies ongoing
- Station 1 gain homogeneity
- RPC life-time
- Some production already started and the remaining should begin in 2003