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

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…

The ALICE experiment (LHC-CERN) A Large Ion Collider Experiment y LHC-CERN 2007 Collisions: p-p ( = 14 TeV) Heavy ions ( = 5.5 TeV per nucleon pair) Muon Spectrometer (-4 < y < -2.5) Vertex information

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) 416-422.

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 ...

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

Design of the Muon Spectrometer Iron Wall Pipe Shield Station 1-2 (tracking) Station 3-4-5 (tracking) Front Absorber Station 6&7 (trigger) Dipole Magnet

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.

Frontal Absorber 90 cm

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

Muon trigger system Compromise between quarkonia efficiency and background rejection: soft background hadronic muons open heavy flavor decay Reducing trigger rates below 1kHz: PbPb @ LHC ~8kHz, CaCa @ 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

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

Trigger Detectors RPC prototype Torino RPCs installed in ALICE

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

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

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 mm2 to 5 x 30 mm2 CPC Prototype from Orsay

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

Momentum Resolution A. Zintchenko Work Kh. Boudjemline PhD thesis

Acceptance and efficiency Track reconstruction efficiency dNch/dy=2x6000 @ y=0 % of bad tracks A. Zintchenko Work

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.

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) : 0-8 GeV/c J/ high statistics: 0-20 GeV/c ’, (3S) poor significance S. Grygorian Work

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/0507084(2005) PRC72 034906(2005) Good sensitivity J/, (1S) & (2S) S. Grygorian & Ph. Crochet Work

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

Thank you!