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CPC response Simulation of Tracking System of
ALICE Muon Spectrometer
K. Boudjemline, J.-P. Cussonneau, Ch. Finck, M.
Germain, L. Luquin and G. Martinez.SUBATECH
(CNRS-IN2P3, Ecole des Mines de Nantes et
Université de Nantes, France).
ALICE Detector
ALICE (A Large Ion Collider Experiment) is the
only detector dedicated to the study of
nucleus-nucleus interactions at the LHC. It will
investigate the physics of strongly interacting
matter at extreme energy densities, where the
formation of a new phase of matter, the
quark-gluon plasma (QGP), is expected.
Trigger Chambers
Muon Spectrometer
Dipole
Absorber
ALICE is composed of many sub-detectors. Among of
them the forward muon spectrometer which include
absorber, dipole magnet, ten tracking chambers
and two trigger chambers. The aim of the forward
muon arm is to measure the complete spectrum of
heavy quark vector mesons J/ Y, Y, Y, Y, Y
via their muonic (m m-) decay in pp and
heavy-ion collisions. The dissociation of these
resonances is one of the most promising
signatures of QGP formation.
Tracking Chambers
Test Beam
Cathode Pad Chamber
X
Muon chambers are proportional gaseous detectors
(Cathode Pad Chamber). They contain a wire plane
and two cathode planes composed of pads. The
incident particle creates, per ionisation,
primary electrons which drift towards wires under
electric field and acquire sufficient energy for
ionising the gas mixture.
CERN-PS 7 GeV/c pions.CERN-SPS 100 GeV/c
muons. Tracking System 5X and 5Y silicon strips
(resolution15mm). Trigger 4 scintillators. Protot
ype CPC. Ar20CO2 gas, X/X03. Multi-scattering
sPS42mm and sSPS10mm.
Z
This, lead to the creation of electron avalanches
near the wires. The movement of the ions induces
the electric signal obtained on the cathodes.
Simulation
(c)
(b)
(a)
A Simulation code uses Monte-Carlo method and
contains - creation of electrons in the gas
interaction number (Poisson distribution) (a)
electron cluster (Cluster Size distribution)
(b)- drift of electrons toward wires-
multiplication of electrons near the wires (Polya
gain distribution) (c)- charge sharing between
both cathodes- induced charge on cathodes
(Mathieson-Gatti distribution)- addition of
electronic parameters (noise and saturation) for
each pad.
Counts
Counts
Counts
Interaction number
Electrons
Gain
Results Comparison to Experimental Data
Simulation
PS data
Charge on Bending Plane
Charge Sharing
Bending charge/Total charge
Wire pitch 2.5mm
Charge Correlation
Bending charge (ADC channels)
Counts
X position (mm)
Application of angle effect to AliRoot
Non-Bending charge (ADC channels)
Bending charge (ADC channels)
The angle effect is taken into account by adding
fluctuation of charge position along wires to the
one calculated by AliRoot (this fluctuation has
been obtained from the simulation with gaussian
form).
Spatial Resolution
s68mm
The spatial resolution is the sigma of the
gaussian fitted on the residual distribution
(difference between both impact point positions,
extrapolated and reconstructed).
Simulation
s70mm
PS data
Before
Angle 10º
Resolution lt 100mm in Y direction (Bending Plane)
with 25X5mm2 pads
Counts
After
SPS data
Counts
? Intrinsic resolution
Efficiency
Angle effect
Residual (cm)
Simulation
Residual (mm)
Simulation
PS data
SPS data
Before
After
Intrinsic resolution (mm)
Resolution (mm)
Efficiency ()
Intrinsic resolution (mm)
PS data
HV (V)
Angle (degrees)
HV (V)
Angle (degrees)