1. GLD IR optimization and background study
H.Fujishima, Saga-U
ILCWS2007, Beijin
5 February 2007

2. Motivation Geant4 based full simulation (Jupiter)
Anti-DID optimization in GLD
Background hits in GLD detector with 3T solenoid field added anti-DID.
IR optimization (FCAL inner radius)

3. IR Design Hole radius FCAL inner radius Beam crossing angle: 14mrad
Position
R [cm]
Z [cm] A
1.3
4.5 B
3.4 25 C 35 D
8.2
110 E
230 F
9.04
260 G
11.94
285 H 16
320 I
400 J
6.0 K
405 L
430 M
450 N 13 O
17.7 P 36 Q 20
Hole radius
FCAL inner radius
Beam crossing angle: 14mrad

4. Anti-DID Field Solenoid with anti-DID: Bz = 3T, Bx_serpentine
Andrei’s anti-DID data: (z,Bz,Br,Bx_serpentine)
Downstream
Upstream IP
Br_x = r/d*Br*cos(theta)
Br_y = r/d*Br*sin(theta)
d = z*theta
Anti-DID field
Solenoid with anti-DID, X-Z plane

5. Anti-DID Optimization
1.2 times Andrei’s data is the best pass efficiency.
Pair background cluster exits extraction hole. %

6. Background hits with anti-DID
CAIN is used to generate pair background.
Beam parameter is nominal at center of mass energy 500 GeV.
Plain solenoid: 10 bunches
Solenoid with anti-DID: 8 bunches
Background hits are monitored by VTX and TPC. They are simply digitized.
500GeV Nominal で作ったbackground source.

7. Hits in VTX
VTX map
VTX in GLD has 6 layers. It consists of the 5 micron pixel charge coupled device.
The signal of each 1 train is read, and 1 incident particle sound 4 pads on the average.
So tolerance (1% occupancy) is 1.0*10^4 hits/cm^2/train.
tolerance
VTX originについて
Primaryが多いはずなのに、予想以上に減っている？
VTX hitにはanti-DIDは効いてこない
Hits of solenoid field added anti-DID became half compared with it of plain solenoid.
Do VTX hits include much backscatter?
I have to study the origin of VTX hits.

8. Hits in TPC
1 hit in TPC consists of 5 pads (1mm*6mm) * 5 buckets (50nsec).
Tolerance of TPC (0.5% occupancy) is 5*10^5 hits/50micro second.
Hits of solenoid field added anti-DID is about 1/3 compared with it of plain solenoid.
It is because backscatter decreased.
tolerance
Pad 約100万
Pad * (50musec / 50nsec * 2) / (5buckets * 5pads/hit)

9. IR Optimization FCAL inner radius for TPC background hits.
Hole radius of extraction to decrease backscattering.
Radius of beam
Optimizationの全体の流れ
そのうちFCALのinner radiusについて取り上げる
Hole radius
FCAL inner radius

10. FCAL Inner Radius Optimization
The purpose is to optimize forward calorimeter (FCAL) inner radius to decrease TPC background.
Default value of FCAL inner radius was determined by simple head on geometry.
But… we have to verify it by full simulation.
FCAL
CH2Mask
BCAL
FCAL Inner Radius
Support Tube

11. Treatment of TPC hits There are continuous hits in the z direction.
These are made by 1 incident particle.
Estimation by the number of incidence particle.
About 3 bunches are used.

12. Preliminary Result Results are written by 4 kinds of radiuses.
82 mm is standard.
No dependency is seen.
Statistics is not enough because of necessity a lot of time.

13. Summary Anti-DID field is optimized. → Background hits are reduced.
IR optimization has been started. FCAL inner radius is under study now.