Velo Software Status: Material, Si Simulation

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VeloSoftware StatusMaterial,Si
Simulation
Chris Parkes Juan Palacios
Thanks to Thomas, Niels for checks/ feedback
Velo Meeting, LHCb week Cambridge, September 18th
2002
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Event Data Model
MC Velo Hit
MC Velo FE
VeloCluster
VeloDataProc
VeloSim
VeloFullDigit
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Silicon Simulation

• Signal simulation
• Noise simulation
• Capacitive coupling
• Spill Over
• Repeat previous two steps with min. bias event
• All results multiplied by factor (30)

Inspired by Patricks simulation (IPHE
2001-001) CDF simulation notes ( CDFR/4914)
Algorithms NOT yet thoroughly compared with
test-beam data
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Signal simulation

• Allocate charge along particle path
• According to n strips passed through
• inhomogeneous charge distribution from delta rays
• Diffuse Charge to neighbouring strips
• Sigma sqrt(2kTthicknessdZ/qV) 7um

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Noise Simulation

• All strips with signal get noise
• Other strips above a threshold
• Generate random numbers from Gaussian tail
• Noise sigma
• Constant term ? strip capacitance

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Capacitive Coupling

• Test-Beam Data
• (Franks note LHCb-VELO 2000-99)
• Also CDF measurements
• 5 coupling between strips
• Charge allocated to neighbouring strips

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• 4000 FE s/Evt with 4500 e threshold
• 50 Signal
• 25 Noise

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Relations

• VELO Cluster -gt MCParticle/MCHit
• MCVeloFE contains list of MCHits
• New version also contains deposited charge of
  MCHits
• Relations rewritten to add multiple MCHits in
  Cluster
• Allows correct identification for Clusters/FE s
  containing hits from multiple particles (1
  level)
• For SpillOver we do not store MCHits
• Though for debugging it would be rather useful.

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Noise
Noise in signal dominated strips
Noise (electrons)

• 1500 electrons to all strips with signal random
  noise strips

Noise in Noise dominated strips
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ADC Sum for Clusters (SN 31)
8 bit ADC No pedestal added
Noise Clusters
Signal

• 1700 Clusters/Evt
• 70 signal

ADC counts
Current setting is 51
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Efficiency for reconstructing Clusters99.9
R (cm)
Z (cm)

• Losses due to clustering problems at region
  boundaries
• Needs modification to Det Element

R (cm)
Z (cm)
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Resolution
N strips

• Shows similar behaviour to
• full simulation of Patrick
• Test beam measurement

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Material DescriptionMaterial Description

• So good, Juan had to do it twice
• Sicb
• Used for simulation in GEANT3
• XML
• Used by tracking to calculate
• material passed through
• Eventually will use for Geant4

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Material radiation lengths

• Sicb
• XML

Radiation lengths
Phi
?
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Material ratio of two

• First test
• Broadly similar
• Some discrepancies expected
• (e.g. from missing shapes in XML)
• Further checks/ mods being performed
• (e.g. double thickness hybrid components)

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Material Comparison
2lt?lt5 , -?/2 lt ? lt ?/2

• DetDescChecks
• Overlap free
• introduce gaps, due to precision problems
• Material
• (mod to be flat in ?)
• Need C option to turn on/off individual
  components

• Exit window, beam pipe connection now in
  Velo2Rich1

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To Do List

• Finalize for TDR production
• By end of October
• Consider 45 degree sectors ?
• On similar timescale.
• Alignment Algorithms
• Paula, Themis, Juan CP
• Duplicate Test-beam problems ?
• What mechanical tolerances are required ?
• What algorithms ?
• How fast ?
• What is effect on physics ?
• Read in test-beam data
• Compare with simulation
• Aim to move all test-beam analysis to GAUDI
• Anyone want to work on this ?