1. Design and performance of the ALICE Muon Spectrometer
Martino Gagliardi
University & INFN, Turin
for the ALICE collaboration
International Workshop High Energy QCD ECT, Trento, January 9th-13th 2007
Design and performance of the ALICE Muon Spectrometer

2. Outline The ALICE Muon Spectrometer; physics goals
Design of the ALICE Muon Spectrometer:
Physics performance of the Alice Muon Spectrometer
- Absorbers - Dipole magnet - Trigger system - Tracking system
Efficiency and resolution - Quarkonia detection - Suppression scenarii - More…

3. The ALICE experiment (LHC-CERN)
A Large Ion Collider Experiment y
LHC-CERN Collisions: p-p
( = 14 TeV)
Heavy ions
( = 5.5 TeV per nucleon pair)
Muon Spectrometer (-4 < y < -2.5)
Vertex information

4. The ALICE Muon Spectrometer
BEAM SHIELDING (W)
FRONT ABSORBER (composite material)
m FILTER (Fe)
TRACKING SYSTEM (Cathode Strip Chambers)
TRIGGER DETECTORS
(Resistive Plate Chambers)
DIPOLE MAGNET
B = 0.7 T
Designed to study heavy quarkonia production (e.g. J/, ) in A-A and p-p collisions through their decay in +-- pairs: suppression of such resonances is among the expected experimental signatures of QGP formation*.
Anomalous J/ production observed at SPS and RHIC: picture is not clear: Regeneration? Sequential melting?
* T. Matsui e H. Satz, Physics Letters B 178 (1986)

5. Physics Goals
Studying heavy quark production via their muonic and semi-muonic decay.
Forward rapidity (-4 < y < -2.5), xBj  10-5
Large quarkonia acceptance down to pT  0
Measurement of Quarkonia production - as a function of centrality (ZDC) - as a function of pT, rapidity - for different colliding systems (including p-A) - versus other observables : vertex properties, electrons, global observables ...

6. A challenging task Separation between bottomonia resonances:
M(2S)-M(1S)= 563 MeV/c2
M(3S)-M(2S)= 332 MeV/c2
(1S)
(2S)
(3S)

7. Design of the Muon Spectrometer
Iron Wall
Pipe Shield
Station 1-2 (tracking)
Station (tracking)
Front Absorber
Station 6&7 (trigger)
Dipole Magnet

8. Absorbers Front Absorber (-4.0 < <2.5, I~10):
Reducing forward flux of charged particles.
Decreasing the hadronic muon background (limit of 90 cm to IP due to the central barrel).
Minimizing multiple scattering and straggling.
Beam shield (-7 < <-4):
Reducing low energy background from the pipe
Iron wall (-4.0 < <-2.5, I~7.2):
Reducing low energy background in the trigger chambers which are less constrained by multiple scattering.

9. Frontal Absorber
90 cm

10. Muon Dipole Magnet Warm dipole (~ 4MW) 820 tons B=0.7 T, ∫Bdl ~ 3 TmBx
Bending Plane yz
Non-Bending Plane xz
Warm dipole (~ 4MW)
820 tons
B=0.7 T, ∫Bdl ~ 3 Tm

11. Muon trigger system
Compromise between quarkonia efficiency and background rejection:
soft background
hadronic muons
open heavy flavor decay
Reducing trigger rates below 1kHz:
LHC ~8kHz,
LHC ~30kHz
Fast decision (<1s) for pT cut:
High pT (~2 GeV) for 's
Low pT (~1GeV) for J/
pT estimated from deviation in magnetic field, measured by the trigger stations

12. Trigger detectors (Resistive Plate Chambers)
Each trigger station is made of two planes of 18 Resistive Plate Chambers each.
~ 6.5 m
2 mm
~ 5.5 m
Muon efficiency  95%
Fast response ( 2 ns)
Time resolution  1 ns (ADULT signal discrmination technique)
Rate capability 100 Hz/cm2 ( low resistivity electrodes)
Spatial resolution  1 cm

13. Trigger Detectors
RPC prototype Torino
RPCs installed in ALICE

14. Trigger Rates and Efficiency
PbPb (8kHz)
Low pT: ~0.5 kHz, J/y efficiency ~ 70%
High pT: ~90 Hz,  efficiency ~95%
CaCa (30kHz)
Low pT: ~0.8 kHz, J/y efficiency ~ 70%
High pT: ~60 Hz,  efficiency ~95%
pp (200kHz)
Low pT: ~10 Hz, J/y efficiency ~ 70%
High pT: ~ very low,  efficiency ~95%
F. Guerin and F. Yermia PhD thesis

15. Muon Tracking System Five stations for tracking:
From z = - 5 m to z = -14 m and from 1.8 m to 5.6 m radius.
Two detection planes for each station.
Detection plane consists of Multi wire proportional chambers with bi-cathode pad readout: bending and non-bending.
Spatial resolution below 100 m in the bending plane, around 700 mm in the non-bending plane
4 Cathode Pad Chambers sectors for Station 1 & 2; 18 CPC slats for Station 3 and 26 for Station 4 & 5.
Pad plane X
Gas Ar+(20%)CO2
5 mm
Wire plane
2.5 mm
Pad plane Z

16. Stations 1 and 2: quadrants
8 CPCs for Station 1
more than 60,000 channels
Similar CPCs for St.2
Cathode pad size ranging from 4 x 6 mm to 5 x 30 mm2
CPC Prototype from Orsay

17. Stations 3, 4, 5: slats 140 CPC slats (19 types)
Lengths from 80 cm to 2.4 m
Cathode pad size from 5 x 25 mm2 to 5 x 100 mm2
Cagliari, Gatchina, Nantes, Saclay

18. Momentum Resolution
A. Zintchenko Work
Kh. Boudjemline PhD thesis

19. Acceptance and efficiency
Track reconstruction efficiency
y=0
% of bad tracks
A. Zintchenko Work

20. Mass Resolution Resolution with nominal BKG  100 MeV (70 MeV)
A. Zintchenko Work
Resolution with nominal BKG  100 MeV (70 MeV)
for  (J/y). Vertex position from ITS needed.

21. PbPb cent, 0 fm<b<3 fm
Quarkonia  +-
PbPb cent, 0 fm<b<3 fm
S/(S+B)1/2
S/B
B[103]
S[103]
State
8.1
0.48
0.42
0.20
(3S) 12
0.65
0.54
0.35
(2S) 29
1.7
0.8
1.3
(1S)
6.7
0.01
300
3.7 ’
150
680
130
J/
Baseline yields (106 s data taking)
(1S) & (2S) : GeV/c
J/ high statistics: 0-20 GeV/c
’, (3S) poor significance
S. Grygorian Work

22. Suppression Scenarii S. Grygorian & Ph. Crochet Work Suppression-1
Tc =270 MeV
D/Tc=1.7 for J/
D/Tc= 4.0 for .
Suppression-2
Tc=190 MeV
D/Tc=1.21 for J/
D/Tc= 2.9 for .
Hep-ph/ (2005)
PRC (2005)
Good sensitivity
J/, (1S) & (2S)
S. Grygorian
&
Ph. Crochet Work

23. And more … Heavy quarkonia measurements in pp
Measurement of the J/y polarization
Open beauty measurements
Low masses
Electro weak boson measurements …

24. Thank you!