# Presentation: 363174

## Jan Balewski, MIT
FGT Project Review
January 7-8, 2008

- Jan Balewski, MIT
- FGT Project Review
- January 7-8, 2008

-  Detector requirements
-  Disk layout
-  e+/e- separation
-  e/h discrimination
-  Simu GEM response
-  Strip layout, occupancy
-  To-do- list
-  Summary

- FGT Layout  Simulation Results

** ****e+ shower**
** ****E****T****=40 GeV**

## FGT Requirements

-  Reconstruct charge of e+, e- from W decay for PT up to 40 GeV/c
-  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

## Optimization of FGT Disks Location in Z

-  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

## Optimization of FGT Disk Radii 

**Rxy – Z  representation**

**Rxy – ********  representation**

**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

## Optimization of FGT Disk Radii (& location)

- R-’unconstrained’
-  FGT  disks

- FGT disks
- fitting in
-  available
-  R-space

- Critical FGT coverage depends on Z-vertex

- FGT disks geometry:  Rin=7.5cm, Rout=41cm,  Z1...Z6=60...150cm, Z=18cm

## FGT Enables Reco of Sign of e+,e-

- FGT Enables _Reco of Sign_ of e+,e-

- 100cm

- Y/cm

- 40cm

- 20cm

- X/mm

- 1.0

**Vertex**
******=200******m

**Endcap SMD**
- hit** ********=1.5mm**

- reco track 

- Limit for  pT  track

**3 FGT hits**
******=70******m

- 0

- 2.0 mm

**Sagitta=2mm**

**Wrong Q-sign**

**Good Q-sign**

## Track & Charge Sign Reco Efficiency

- FGT disks geometry:  Rin=7.5cm, Rout=41cm,  Z1...Z6=60...150cm, Z=18cm

**N0 – thrown electrons, E****T****=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**

## Stability of Charge Reconstruction

- Studied variations of efficiency (shown in proposal):
-  degraded FGT cluster resolution (80m  120m, OK)
-  reduced # of FGT planes (6 4 , bad, too few hits/track)
-  degraded transverse vertex accuracy (200m 500m, OK)
-  FGT cluster finding efficiency (100%  90%, OK , _[details](http://www.star.bnl.gov/public/eemc/TUP-study/UPGR05_eval/take5_chargeReco_PT30GeV_more/)__)_
-  **smaller FGT disk size & separation - OK**

- Rin=18cm, Rout=37.6cm,
- Z1...Z6=70...120cm, Z=10cm

## e/h Discrimination Capability of Endcap EMC

**Projective tower**

- Shower from electron
- E=30 GeV  

- Simu of Endcap response to
**Electrons (black)** &
**charge pions (red)** with ET of 30 GeV

**Endcap**

******+**

**e+**

******+**

**e+**

- ~15 GeV
- ET Trigger
- threshold

## e/h Discrimination : PYTHIA Events

**Hadrons from **
**PYTHIA M-C**
**QCD events**

**e+, e- from **
**PYTHIA M-C**
**W-events**

**Isolation & missing-PT cuts**
**suppress hadrons by ~100**

## Real Electrons Reconstructed in Endcap

**Identified e+,e-**

## Detailed Simulation of GEM Response (1)

**ionization and charge amplification**
** ****spatial quantization on GEM grid**
** ****charge collection by strip planes**
** ****1D cluster reconstruction**

## Simulated FGT Response (2)

**GEM response**

**1D Cluster finder resolution**

**Test beam data**

## FGT Strip Layout *)

**Top ********-layer**
**949 ********-strips**
**pitch 600********m**

- *) close to final

******Essential for P****T**** reco**
** ****~ 50% transparency**

****** ****needed for 3D**
** ****track recognition,**
** ****resolving ambiguities**

**FGT quadrant **
**boundaries**
**match to **
**Endcap **
**segmentation**

**Bottom R-layer**
**pitch 800********m**

## Estimation of Strip Occupancy

-  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**

## 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

## FGT Simulation Summary

-  **Will be able** to reconstruct charge of e+, e- from W decay for PT up to 40 GeV/c **with efficiency above 80%**
-  **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

## BACKUP

## Compact FGT- proof of principle

- Critical FGT coverage depends on Z-vertex

- Rin=18cm, Rout=37.6cm, Z1=70cm, ...,Z6=120cm, Z=10 cm

## FGT Material budget UPGR13, maxR=45 cm

- Z vert= - 30cm

- Z vert= 0cm

- Z vert= + 30cm

**0**

**0.5**

**0**

**0.5**

## FGT Material UPGR13 w/o SSD

## TPC reco with 5 points

**‘****regular’ tracking**
**5-hits tracking**

**‘****regular’ tracking**
**5-hits tracking**

## Alternative Snow-flake Strip Layout

- As in
- Proposal 

-  12-fold local
- Cartesian
- ref frame

## Track Reco Strategy

- Select EMC cluster with large energy
- Eliminate all FGT hits outside the cone: vertex SMD hit
- Resolve remaining ambiguities comparing R vs.  charge
- Consider shorter -strips (snow flake design)

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