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Jan Balewski, MITFGT Project ReviewJanuary 7-8, 2008
• Detector requirements• Disk layout• e+/e- separation• e/h discrimination• Simu GEM response• Strip layout, occupancy• To-do- list• Summary
1 2 3 4 5 6 FGT disks
=1.0
=1.5
=2.0
FGT Layout Simulation Results
e+ shower ET=40 GeV
2FGT Layout and SimulationsJan Balewski, MIT
FGT Requirements
1. Reconstruct charge of e+, e- from W decay for PT up to 40 GeV/c
2. Discriminate electrons against hadrons
• Allow for uniform performance for z-vertex spread over [-30,+30] cm• Fit in geometrical space free up by the West Forward TPC (FTPC)• Benefit from limited coverage of other trackers: IST, SSD• Relay on vertex reconstruction and Endcap shower-max hit• Relay on Endcap towers for energy reconstruction• Minimize amount of material on the path of tracks• Align FGT segmentation with TPC sector boundaries and Endcap halves• Assure relative alignment vs. TPC is double with real particles
3FGT Layout and SimulationsJan Balewski, MIT
Optimization of FGT Disks Location in Z
Used TPC volumenHits>=5
SSDIST1,2beam
Zvertex=+30cm
Zvertex=0cm
1 2 3 4 5 6 R-‘unconstrained’ FGT disks
1 2 3 4 5 6 1 2 3 4 5 6
a)
b) c)Zvertex=-30cm
=1.0
=1.5
=2.0
En
dca
pE
MC
Barrel EMC
• 5 hits required for helix reco
• FGT sustains tracking if TPC provides below 5 hits
• use TPC, SSD,IST for Zvertex <~0 and <~1.3
• allow Zvertex[-30,+30]cm
FGT disks geometry: Rin=7.5cm, Rout=41cm, Z1…Z6=60…150cm, Z=18cm
4FGT Layout and SimulationsJan Balewski, MIT
Optimization of FGT Disk Radii (Z Vertex = 0 cm )
Rxy – Z representation
TPCIf nHit>5 EndcapSMD
IST1,2
SSD
FGT 1 2 3 4 5 6
vertex
=1.
7
Rxy – representation
Used TPC volume
nHits>=5
=1.
0=
1.5
=2.0
En
dca
p
Zver=0cm
1 2 3 4 5 6 FGT
trac
k = 1
.7
Optimization Criteria
•Each track must cross the vertex and Endcap EMC
•6 FGT disk are needed to provide enough hits for tracks at all and all z-vertex
•Single track crosses less than 6 FGT disks
5FGT Layout and SimulationsJan Balewski, MIT
Optimization of FGT Disk Radii (& location)
TPCIf nHit>5 EndcapSMD
IST1,2
SSD
FGT 1 2 3 4 5 6
vertex
a) Z Vertex = - 30 cm b) Z Vertex = 0 cm c) Z Vertex = + 30 cm
R-’unco
nstrained’
FGT d
isks
FGT disksfitting in available R-space
Critical FGT coverage depends on Z-vertex
FGT disks geometry: Rin=7.5cm, Rout=41cm, Z1…Z6=60…150cm, Z=18cm11.5 37.5 70
6FGT Layout and SimulationsJan Balewski, MIT
1 of reco track
FGT Enables Reco of Sign of e+,e-
2mm
Sag
itta
(m
m)
100cm
Y/cm
40cm
20cm
X/mm
1.0Vertex=200m
Endcap SMDhit =1.5mm
reco track
Lim
it fo
r p T
tra
ck
3 FGT hits=70m
0
Sag
itta
(m
m)
2mm
2.0 mm
Sagitta=2mm
Wrong Q-signGood Q-sign
7FGT Layout and SimulationsJan Balewski, MIT
Track & Charge Sign Reco EfficiencyFGT disks geometry: Rin=7.5cm, Rout=41cm, Z1…Z6=60…150cm, Z=18cm
N0 – thrown electrons, ET=30 GeV
N1 – reco tracks (<3 mrad) N2 – reco tracks w/ correct charge sign
•Track reco efficiency >80% for up to 2.0•Wrong charge reco <20% for above 1.5
8FGT Layout and SimulationsJan Balewski, MIT
Zvert=0
Stability of Charge Reconstruction
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)- degraded transverse vertex accuracy (200m 500m, OK)- FGT cluster finding efficiency (100% 90%, OK , details)
- smaller FGT disk size & separation - OK
Rin=18cm, Rout=37.6cm, Z1…Z6=70…120cm, Z=10cm
9FGT Layout and SimulationsJan Balewski, MIT
GeV
e/h Discrimination Capability of Endcap EMC
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
10FGT 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
11FGT Layout and SimulationsJan Balewski, MIT
Real Electrons Reconstructed in Endcap
e+, e-
M
IP
TPC P [6,8] GeV/c
e+, e-
MIP
TPC P [10,14] GeV/c
Endcap-based cuts Identified e+,e-
12FGT Layout and SimulationsJan Balewski, MIT
Detailed Simulation of GEM Response (1)1. ionization and charge amplification2. spatial quantization on GEM grid3. charge collection by strip planes4. 1D cluster reconstruction
Primaryionization
Amplified signal is displaced
Hole in GEM foil amplifies charge
cloud
phi-axis strippitch=600m
R-a
xis
strip
Pitc
h=80
0m
x hit
Latice attractorsspaced 130 m
Charge from this hexagon is attracted by the hole
best
13FGT Layout and SimulationsJan Balewski, MIT
Simulated FGT Response (2)
22 eV/pair
(760 eV/ track)14 prim pairs/track
32 any pairs/track
22 eV/pair 14 prim pairs/track
R=122mR*=40m
GE
M r
esp
on
se1D
Clu
ster
fin
der
res
olu
tio
n Test beam data
14FGT Layout and SimulationsJan Balewski, MIT
FGT Strip Layout *)32
6 R
-str
ips
Top -layer949 -stripspitch 600m
x
y
Xz 15 deg
Endcap halves
y
x
*) close to final
Essential for PT reco
~ 50% transparency
needed for 3D track recognition, resolving ambiguities
FGT quadrant boundariesmatch to Endcap
segmentation
Bottom R-layerpitch 800m
15FGT 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 tracks 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
16FGT 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
• 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
17FGT 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
18FGT Layout and SimulationsJan Balewski, MIT
BACKUP
19FGT Layout and SimulationsJan Balewski, MIT
Compact FGT- proof of principle
Critical FGT coverage depends on Z-vertex
Rin=18cm, Rout=37.6cm, Z1=70cm, …,Z6=120cm, Z=10 cm
20FGT Layout and SimulationsJan Balewski, MIT
FGT Material budget UPGR13, maxR=45 cm
Z vert= - 30cm Z vert= 0cm Z vert= + 30cm
0
0.5
0
0.5
21FGT Layout and SimulationsJan Balewski, MIT
FGT Material UPGR13 w/o SSD
22FGT Layout and SimulationsJan Balewski, MIT
TPC reco with 5 points
‘regular’ tracking5-hits tracking
‘regular’ tracking5-hits tracking
23FGT Layout and SimulationsJan Balewski, MIT
Alternative Snow-flake Strip Layout
As in Proposal
12-fold localCartesianref frame
24FGT Layout and SimulationsJan Balewski, MIT
Track Reco Strategy1. Select EMC cluster with large energy
2. Eliminate all FGT hits outside the cone: vertex SMD hit
3. Resolve remaining ambiguities comparing R vs. charge
4. Consider shorter -strips (snow flake design)
1 2 3 4 5 6 FGT
1
2
3
4