performance studies of the cbm silicon tracking system
DESCRIPTION
Performance studies of the CBM Silicon Tracking System. Anna Kotynia Hic for Fair, F rankfurt U niversity. Silicon Tracking System in CBM experiment. The CBM experiment at FAIR will investigate the QCD phase diagram at high baryon densities - PowerPoint PPT PresentationTRANSCRIPT
Anna Kotynia - Silicon Tracking System in CBM experiment
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Performance studies of the CBM Silicon Tracking System
Anna KotyniaHic for Fair, Frankfurt University
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Silicon Tracking System in CBM experiment
The CBM experiment at FAIR will investigate the QCD phase diagram at high baryon densities
The Silicon Tracking System is the central detector for track and momentum determination
Dipol magnetTargetMVD & STS
Anna Kotynia - Silicon Tracking System in CBM experiment
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Silicon Tracking System
Anna Kotynia - Silicon Tracking System in CBM experiment
Chellanges: 10 MHz interaction rate Up to 1000 charged particles per one
Au+Au central collision at 25 A GeV Track densities up to 30 per cm2
Conditions: Highly granular , low-mass and
radiation hard detector system Fast data acquisition system for
online event selection Efficient charged particle tracking
and high momentum resolution
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STS layout
Anna Kotynia - Silicon Tracking System in CBM experiment
Total area, 8 stations: 3.2 m2
Number of sensors: >1000 Number of r/o channels: 1.5M Number of FE chips: >12k
Sensors: 300 µm thick; 6 cm wide; 2-6 cm high.
Outer regions covered by larger sensors, or even chained sensors (1-3 sensors in one module), to minimize number of channels
1024 strips per sensor; 15° stereo angle; 60 µm pitch strip.
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STS Digitizer
Anna Kotynia - Silicon Tracking System in CBM experiment
Complete chain of physical processes caused by charged particle traversing the detector
Magnetic field influances collection of the charge on the strips
|B| = 1THoles:Q = 1.5°Dx = 8mm
ElectronsQ = 7.5°Dx = 40mm
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STS Digitizer
Anna Kotynia - Silicon Tracking System in CBM experiment
Particle position in the sensor is obtain by using Center Of Gravity algorithm:
n
ii
n
iii
S
xSx
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1
Random noise is added to the charge signal, according to a Gaussian distribution with standard deviation as an equivalent noise charge of the detector system
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Hit Finding Efficiency
Anna Kotynia - Silicon Tracking System in CBM experiment
Center Of Gravity method results in a strong dependence of the hit finding efficiency on the particle crossing angle
Hit finding efficiency:54-99% ~92%
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Channel inefficiencies
Single channel inefficiencies as a result of the readout electronic’s dead time
Dependence of channel dead time on pulse amplitude
Anna Kotynia - Silicon Tracking System in CBM experiment
Pulse amplitude [V]
Pulse amplitude [fC]
Pulse length [ns]
0,57 1,70 8100,97 2,58 11001,17 3,47 12201,5 4,45 13802,3 6,80 17302,6 7,70 18403,0 8,91 19803,4 10,10 21304,2 12,47 24105,0 14,85 2670
0 2 4 6 8 10 12 14 160
500
1000
1500
2000
2500
3000
pulse length [ns]
Pulse amplitude [fC]
Pul
se le
nth
[ns]
Preliminary STS simulations results
• Max channel occupancy is 14 times per 100 mbias events • Mostly it is 9~8 times per 100 mbias events
• -> less then 1,25 us time distance between hits in one channel
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Anna Kotynia - Silicon Tracking System in CBM experiment
Channel inefficiencies
Station 1 2 3 4 5 6 7 8
min occ % 0.1 0.1 0.1 0.3 0.2 0.1 0.1 0.1
max occ % 4.7 4.2 3.6 3.0 2.4 2.0 1.3 1.2
Channel dead time
Channel occupancy
Hit finding efficiency
occ>3.0 %(<1% of all chips)
1.0 %<occ>3.0 %(12% of all chips)
occ<1.0 %(88% of all chips)
Probability of channel inefficiency
100 ns >3 % 1-3% < 1% 89.94 %
500 ns >15 % 5-15 % < 5 % 83.37 %
1000 ns >30 % 10-30 % <10 % 78.25 %
0 ns 91.17 %
For minimum bias Au+Au collision at 25AGeV channel occupancy:
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Summary
Anna Kotynia - Silicon Tracking System in CBM experiment
• CBM requirements for the Silicon Tracking System call for a highly granular, low-mass and radiation hard detector system;
• The performance of the Silicon Tracking System has been evaluated with realistic detector responce functions inplemented;
• As a result of implementation of all realistic functions, hit finding efficiency drops down by 2% for particles with incident angle below 20°.
Next Steps Detailed studies of influence of noise level, ADC resolution and channel inefficiencies on
full particles reconstruction; Improvement of STS geometry in order to achieve more then 90% of particles with
incident angle below 20°; Comparision of simulations results with real date obtain from test experiments.