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
    TPC *) Endcap
    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.