Download - The TPC/HBD Simulation Package in PISA
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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The TPC/HBD Simulation Package
in PISA
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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70 cm 20 cm
70 cm
HBD TPCThe TPC/HBD in PISA
Cerenkov radiation from 100 MeV e-
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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What has been done with it so far?
• Occupancy studies• Cerenkov blob size, # photoelectrons
– CH4 and CF4 both implemented as gas options– Blobs in various field configurations
• Multiplicity and conversion studies (with Si upgrade)– Combinatorial background studies: see K.
Ozawa’s talk
• A first look at dE/dx
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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Occupancy of TPC
Innermost pad row (r = 20 cm)90o = 157 divisions in
Central Au-Au (dNch/dy = 650) at 200 GeVAssume 2x10 mm2 pads on readout planes
Midrange pad row (r = 35 cm)90o = 275 divisions in
137 hits199 hits
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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HBD Occupancy, Blob Size
Different colors = different tracks
Occupancy of HBDAssuming 4% of a radiation length from proposed silicon vertex detector upgrade
CF4: ~30 photoelectrons per e- track Blob diameter ~5 cm with zero-integral field
Nphotoelectrons/track
Cou
nts
Central Au-Au (dNch/dy = 650)
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-dependence of blob spread
65o 70o 75o 80o 85o
Looking at a limited region
50 MeV e- at different , zero-integral field
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50 MeV e- getting turned around in the outer PHENIX field
= 85o
Zero-integral field
Turnaround a problem for low-energy electrons at polar angles close to 90o!
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Dalitz pair Cerenkov blobs in different fieldsNo field
Dalitz pairs
Zero-integral Strong (additive)
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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Electron Multiplicities/Event
Averaged over 200 events No Si SiTracking down to 1 MeV 33.7 89.5Tracking down to 10 MeV 30.5 81.4Tracking down to 20 MeV 27.0 73.5
Averaged over 200 events No Si SiTracking down to 1 MeV 28.4 59.8Tracking down to 10 MeV 25.3 56.5Tracking down to 20 MeV 22.6 51.6
In TPC
No min. hits/track required in TPC
Hitting HBD
• Zero-integral magnetic field• 4 layers 1%X0 Si• 4 layers 2%X0 Si: 89.5 130.4 electrons/event in TPC!
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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z (cm)
r (cm
)
Si barrel and endcaps Beampipe
Nosecone
TPC readoutplane
Conversions from “primary” (i.e. 0) photons only
4 layers 1%X0 Si
Vertex of conversion pairs hitting TPC
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dE/dx
• A quick look at dE/dx for electrons in CF4 according to GEANT– value given in
Weizmann Technical Note: ~7 keV/cm
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New inner field coil: low-field inner tracking region for low-momentum measurements
Even with maximum cancellation, not a field-free region
Large Br componentswould make track-finding in TPC difficult! Another field map with 80% cancellation has been requested.
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Plans for the Future• Study track-finding and momentum resolution in TPC for
various partial cancellation field configurations– What distortions in the tracks will there be due to ExB effects in the
non-uniform magnetic field, space charge, . . .?• More realistic detector response and readout• Study HBD segmentation • Investigate alternative gases/gas mixtures• Further integration with proposed silicon upgrade detector
Various documentation on the TPC/HBD in PISA can be found at http://www.phenix.bnl.gov/phenix/WWW/p/draft/caidala/documentation/hbd_tpc/
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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Spare Slides
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TPC Acceptance
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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50 MeV e- at different
65o 70o 75o 80o 85o
Looking at full azimuthal coverage.The particles at 80 and 85o are exiting and re-entering multiple times!
Zero-integral field
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How does the field affect the Cerenkov blobs on the HBD?
No field Zero-integral field
CH4 radiator 200 MeV e- : Little effect
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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With zero-integral field
100 MeV e- 50 MeV e-
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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e+- Multiplicities/event: Effect of no field
Averaged over 200 events No Si Si
No field (Tracking down to 1 MeV)
24.4 80.2
Field(Tracking down to 1 MeV)
33.7 89.5
No min. hits/track required in TPC
Averaged over 200 events No Si Si
No field (Tracking down to 1 MeV)
19.5 50.1
Field(Tracking down to 1 MeV)
28.4 59.8
TPC HBD
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C. Aidala -- Mini Workshop on PHENIX Upgrade Plans -- 8/6/02
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Track distortions due to ExB effectsStandard PHENIX fie ld
20.00
25.00
30.00
35.00
40.00
45.00
50.00
55.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
x (cm )
y (c
m)
Original track
z = 0.0 cm
z = 10.0 cm
z = 20.0 cm
z = 30.0 cm
20% standard PHENIX field
20.00
25.00
30.00
35.00
40.00
45.00
50.00
55.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70
x (cm)
y (
cm
)
Original track
z = 0.0 cm
z = 10.0 cm
z = 20.0 cm
z = 30.0 cm
•Drift out to |z| = 35 cm•Electric field 1000 V/cm•Standard PHENIX B field
Simulated using adapted standalone STAR code written by Jim Thomas