Optimal Z-location of FGT disks - Study of charge reconstruction for high energy electrons
Updated: Jan 18 12:24:16 EST 2007

All plots on this page are produced for a single electron events with pT of 30 GeV/c.

1. Input: one-electron events.
Generated electrons have fixed pT and zVertex of -30, 0, or +30 cm, and uniform eta and phi distribution. Sample of high pT electrons thrown from different zVertex location over eta range [1,2] are shown here: Z=-30cm , Z=0cm , Z=+30cm.,

2. Assumptions about resolution of detectors.
* Use: Vertex + new FGT + truncated TPC + ESMD

Assumed location & resolution
detector assumed resolution weight of the point Remarks
vertex 200 mu m in X,Y,Z W=1/(200 mu m)^2 added as a hit
FST not used
FGT 60 mu m in X,Y
10 mu in Z
W=1/(60 mu m)^2 4 disks (see plot)
at Z=60,80,100,120 cm
Rxy in [3,40] cm
TPC 1 mm along arc
1 mm in Z
W=1/(1mm)^2 * drop padrow #1 and #13
* drop hits at |Z|>197 cm
Endcap SMD
mock hit *)
1.5 mm in X,Y,Z W=1/(1.5 mm)^2 at xPoint of Geant helix
w/ SMD plane
*) Based on SMD response study by Jim

3. The following detector configuartions have been considered
Config Prim
Vertex
FGT
disks
TPC *) Endcap
SMD
A yes 1234 nH>=4 yes
B yes 123 nH>=4 yes
C yes 1 3 nH>=4 yes
D yes 1 2 nH>=4 yes
E yes 1 nH>=4 yes
F yes none nH>=4 yes
G yes 1234 nH>=4 no
*) if nTPC hits<4 then whole TPC is ignored (all its hits).

4. Each of the detectors provide different # of fit points depending on zVertex, eta, and selected configuration.
detector Configurations
FGT all 4 disks, config=A,G
only disks 1+2, config=D
TPC config=A-G, Note, if nhit<4 TPC is ignored
-
E-SMD config=A-F
sum Circle fit is performed if nHitSum>=5, as marked by the red line.
all 4 disks, config=A,G
only disks 1+2, config=D

5. Quality of the reco 3D tracks (fit of circle+line) is defined based on a difference of the reco direction of primary track at the vertex vs. Geant track direction.

Track reco efficiency is defined as the ratio of# of reco tracks (N1) w/
* nFitP>=5, including vertex as a hit
* delPhi<3 mrad
* delTheta <3 mrad
to the # of generated electrons (N0).

Charge reco efficiency requiers additinal
* the sign of the reco charge is correct. Track counter is N2.
No cut on reco pT is imposed.

6. Resulting track, charge reco efficiency and contamination for electrons w/ pt=30 GeV/c.
Note1, we do not want to be in the yellow sqare.
Note2, the change of trend of the red data at eta=~2 comes from missing IST/HFT in the model. It will disapear once inner barrels are added.
Note3, configurations listed in alphabetical order.
track Eff= N1/N0 charg eff = N2/N0 wrong charge (N2-N1)/N1
Config A, FGT=1234, ESMD=yes
Config B, FGT=123, ESMD=yes
Config C, FGT=1 3, ESMD=yes
Config D, FGT=12, ESMD=yes
Config E, FGT=1, ESMD=yes
Config F, FGT=none, ESMD=yes
Config G, FGT=1234, ESMD=no

7. Conclusions
1. 4 GEM disks are the bare minimum to get reco tracks at eta <2.0 (compare config A with F or B)
2. SMD hit does ot matter for track reco (G vs. A), but will matter for charge reco -below.
3. Not much difference if used GFT disk 1+2 vs. 1+3 (C vs. D)

8. Next steps
1. Increasy TPC hit threshold to 6 or more. Pileup in TPC will be hard to resolve.
2. Add 2 GEM disks. Spread them over Z=[60,135] cm. It allows for some redundancy in fast detector only track reco.