1. Simulation Study for One Tentative Geometry of Luminosity Monitor Detector
Huagen Xu
IKP: T. Randriamalala, J. Ritman and T. Stockmanns
24 June, 2018

2. Outline Brief introduction of this work Simulation study process
Results and Discussion
Summary
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3. 1. Brief introduction of LMD
What having been done:
Basic concept design of Luminosity Detector, double- sided strip silicon sensor to reconstruct theta (thus t).
The reconstructed theta based on double-sided sensor is dominated by small angle scattering, 6.2GeV/c with 300μm silicon sensor.
Thinner sensor is expected but might not be double- sided and only short strip
Motivation for new tentative geometry:
Thinner sensor, 150μm or less
Single-sided strip and with two segments
Theta was determined by strip
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4. Sketch of single sided sensor
Strip on
Left Segment
Beam
50μm
2cm
5cm
5.33 cm
3cm
1. Sensor will cover 3-8mrad, be placed at z=10.8m far from IP
Right Segment
2. Dimension: 2cm x 5.33cm x 5cm x 150μm (thickness)
3. 16 sensors placed at 4 planes, 4 sensors/plane
(up and down, left and right), 20cm between the neighbor planes
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5. 2. Simulation study 2.1 MC simulation Input and Setting:
Geometry definition with ASCII file, including sensor, beam pipe , vacuum box
VMC :
Propagation: Geant3, Geant4, Fluka
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6. Energy loss information Hit position on the detector
Generator: Box Generator, antiproton with momentum 6.2GeV/c coming from(0,0,0), Theta:2-9mrad, Phi: 0-360
MC: TGeant3
Field: None field is on
Events: 10000
Output:
Energy loss information
Hit position on the detector
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7. MC Results MC output will be used as the input of Digitization
MC Hits 3D plot
MC output will be used as the input of Digitization
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8. 2.2 Digitization
To simulate the detector response of the interaction with incident particles
Output: Channel ID, FE module number, Charge, Time etc.
Strip parameters and FEE parameters:
Pitch = 50 μm
Strip structure (e.g. Strip direction, two segments)
Anchor point (start position to count strip number)
Front End Electronics module (e.g. APV25)
FE channels of each module (e.g. 128chs)
Noise (e.g electrons)
Threshold of signal (e.g electrons)
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9. Strip Structure and Charge distribution
Strip on
Left Segment
Right Segment
Anchor Point
Beam
Anchor Point
Here, σ of charge diffusion as a function of sensor thickness, of the sensor)
Charge diffusion was taken into account
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10. Engergy Loss & Digi Charge
Conversion constant between Eloss and electrons = 3.61 (eV/e)
48.21 keV ~ 1.335e+4
1.263e+4 ~ keV
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11. Channel ID, FE module and count of channels
Channel ID, FE Module number and Charge will be used as the input of Reconstruction of hits
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12. 2.3 Reconstruction
Based on the digitized data to calculate the information of incident event.
Left Segment,
Right Segment
Beam
Output: Information of incident event, i.e. hit position, deposited energy etc.
Center of Gravity: If more than 1 strips fired by one hit, it will give more accurate position information
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13. Reconstructed information
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14. MC
Reco
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15. 2.4 Tracking theta determination
Theta determined by strip
Theta resolution : 0.02mrad
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16. Theta determined by fitting 4 Recohits: 0.092mrad
Theta determined by fitting 4 MChits: mrad
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17. 3. Discussion 3.1 Advantage and disadvantage of this geometry
Beam axis θ θ’
Pellet size: 25-40μm
lateral spread σ ≈ 1mm
inter spacing 0.5-5mm
δθ = θ’ - θ
Transversal smearing with σ ≈ 1mm will result in
δθ ≈ 0.1mrad for determined θ
Longitudinal smearing has got little effect, e.g. 5mm result in δθ of 0.003mrad
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18. Theta resolution (by strip) : 0.058mrad
Theta resolution (by fitting 4 Recohits): mrad
Theta resolution (by fitting 4 Mchits) : mrad
Particle emitting from a square area with side of 2mm +1 -1
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19. 3.2 Face the challenge from the solenoid field
Field On
Field Off
3.2 Face the challenge from the solenoid field
BoxGenerator,
Beam Particle: antiProton;
Beam momentum: 1.5GeV/c;
Fixed theta: 5mrad;
Azimuth: 0~360;
MChits XY view
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20. Peak of MCHits Theta RMS of MCHits Theta Field On Field Off On - Off 20
Field On
Field Off
On - Off
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21. 3.3 Beam transverse emittance
Beam transverse emittance: <1 mm mrad
Theta resolution: > 0.3mrad
(simulated based on double-sided sensor,300μm)
By Tsito
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22. 4. Summary
A tentative geometry of LuMo with single-sided strip was studied with PandaRoot framework
The performance of LuMo with single-sided geometry was discussed, the theta resolution would be dominated by the target size;
The final resolution of theta (thus t) would be dominated by beam transverse emittance.
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23. Thanks for your attention!
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