This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Jan Balewski, MITFGT Project ReviewJanuary 7-8, 2008
needed for 3D track recognition, resolving ambiguities
FGT quadrant boundariesmatch to Endcap
segmentation
326
R-s
trip
s
Bottom R-layerpitch 800m
Compact FGTRin=18cm, Rout=37.6cm, Z1=70cm, …,Z6=120cm, Z=10 cm
11FGT Layout and SimulationsJan Balewski, MIT
Estimation of Strip Occupancy
Track rate per strip for minB PYTHIA events @ s500 GeVBased on FGT geometry: Rin=15cm, Rout=41cm
R-strips45 deg long
2
0
1
trac
ks
R=41cm R=15cm =0 deg =90
1 track/strip
per 1000
minB events
trac
ks
0.8
0
0.4
1
-strips 400 m pitch
• pileup from minB events dominates•1.5 minB interactions/RHIC bXing• 300nsec response of APV 3 bXings pile up
Total pileup of 5 minB events per trigger event
• 1 track per FGT quadrant per minB event (scaled from simu below)
• Cluster size: 1mm along , 2mm along R
• Cluster occupancy per triggered event per quadrant • -strips (span ~43cm) 1.2% occupancy• R-strips (span 25cm) 4% occupancy(uncertainty factor of 2)
minB PYTHIA event @ s=500 GeV
12FGT Layout and SimulationsJan Balewski, MIT
e/h Discrimination : PYTHIA Events
Hadrons from PYTHIA M-CQCD events
e+, e- from PYTHIA M-C
W-events
Isolation & missing-PT cutssuppress hadrons by ~100
13FGT Layout and SimulationsJan Balewski, MIT
GeV
e/h Endcap EMC additional factor of 10
Projective tower
PreShowers
PostShower
ShowerMax
Shower from electron
E=30 GeV
=2.0
=1.08
Simu of Endcap response toElectrons (black) & charge pions (red) with ET of 30 GeV
Endcap+
e+
30 GeV0
+ e+
GeV
+
e+
~15 GeVE T Trigger
threshold
14FGT Layout and SimulationsJan Balewski, MIT
e+, e-
M
IP
TPC 6<P<8 GeV/c
e+, e-
MIP
TPC 10<P<14 GeV/c
Endcap-based cuts Identified e+,e- in p+p 2006
Real Electrons Reconstructed in Endcap proof of principle
15FGT Layout and SimulationsJan Balewski, MIT
To-do List
• completion of detailed (a.k.a. ‘slow’) simulator for GEM response
• develop 3D tracking with pattern recognition, integrate w/ STAR tracking
• include pileup from 3 events in reco of physics events
• implement and optimize full array of e/h discrimination techniques
• completion of full W event simulation and comparison to full hadronic QCD
events simulation
• determine background contribution from Z0 and heavy flavor processes, above
pT>20 GeV/c
16FGT Layout and SimulationsJan Balewski, MIT
FGT Simulation Summary
1. Will be able to reconstruct charge of e+, e- from W decay for PT up to 40
GeV/c with efficiency above 80%
2. There is enough information recorded to discriminate electrons against hadrons
• Allow for uniform performance for z-vertex spread over [-30,+30] cm, OK• Will fit in geometrical space• Will use hits from IST, SSD• Will relay on vertex reconstruction and Endcap shower-max hit & energy• FGT quadrants are aligned with TPC sector boundaries and Endcap halves• FGT disks 1 & 2 overlap with TPC allowing relative calibration
17FGT Layout and SimulationsJan Balewski, MIT
BACKUP
18FGT Layout and SimulationsJan Balewski, MIT
Track Reco Strategy1. Select EMC cluster with large energy (ET>15 GeV)
2. Find Endcap SMD cluster location ( x~y~5cm)
3. Find transverse vertex position (x~y~0.2mm)
4. Eliminate all FGT hits outside the cone: vertex SMD hit
5. Resolve remaining ambiguities (if any) by
comparing R vs. charge
1 2 3 4 5 6 FGT
1
3
5
2
4xx
x
19FGT Layout and SimulationsJan Balewski, MIT
TPC reco with 5 points
‘regular’ tracking5-hits tracking
‘regular’ tracking5-hits tracking
20FGT Layout and SimulationsJan Balewski, MIT
Alternative Snow-flake Strip Layout
As in Proposal
12-fold localCartesianref frame
326
R-s
trip
sTop -layer949 -stripspitch 600m
Bottom R-layerpitch 800m
21FGT Layout and SimulationsJan Balewski, MIT
FGT Material budget UPGR13, maxR=45 cm
Z vert= - 30cm Z vert= 0cm Z vert= + 30cm
0
0.5*Xo
0
Non-FGTmaterial upfront
Non-FGTmaterial upfront
Non-FGTmaterial upfront
0.5*Xo
22FGT Layout and SimulationsJan Balewski, MIT
Study of stability of efficiency
Studied variations of efficiency (shown in proposal):
- degraded FGT cluster resolution (80m 120m, OK)
- reduced # of FGT planes (6 4 , bad, too few hits/track)