CLAS12 Drift Chambers Simulation and Event Reconstruction

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CLAS12 Drift Chambers Simulation and Event
Reconstruction

Latifa Elouadrhiri Jefferson Lab
Hall B 12 GeV Upgrade Drift Chamber Review
Jefferson Lab March 6- 8, 2007
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Outline

• CLAS12 Drift Chambers Requirements
• Luminosity Studies
• Two methods occupancy estimation, direct track
  reconstruction
• Results comparison of different methods
• Resolution p, ?, f
• Two methods linearized calculations, track
  simulation and reconstruction
• Results comparison of different methods
• Monte Carlo Simulation of Physics Reactions

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CLAS12 Drift Chambers Requirements
R3
R2
R1
Arrangement of drift chambers in CLAS12
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Background Situation at L1033cm-2s-1, DT 150ns
Drift ChambersR1
No Magnetic Field
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Background Situation at L1035cm-2s-1, DT 150ns
No Magnetic Field
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CLAS12 Single sector (exploded view)
CLAS 12 Solenoid provides magnetic field for
guiding Møller electrons away from detectors.
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Solenoid Requirements
CLAS12

• Provide magnetic field for charged particle
  tracking for CLAS12 in the polar angle range from
  40o to 135o.
• Provide magnetic field for guiding Møller
  electrons away from detectors.
• Allow operation of longitudinally polarized
  target at magnetic fields of up to 5 Tesla, with
  field in-homogeneity of ?B/B lt 10-4 in cylinder
  of 5cm x 3cm.
• Provide full coverage in azimuth for tracking.
• Sufficient space for particle identification
  through time-of-flight measurements.
• Minimize the stray field at the PMTs of the
  Cerenkov Counter
• Minimize the forces created by one magnet on the
  other

CLAS12 Solenoid
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Solenoid Requirements
CLAS12

• CLAS 12 Solenoid provides magnetic field for
  guiding Møller electrons away from detectors.

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Background Situation at L1035cm-2s-1, DT 150ns
No Magnetic Field
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Background Situation at L1035cm-2s-1, DT 150ns
Electrons
Photons
One Event
with 5 T Magnetic Field
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Møller Electrons in 5 Tesla Solenoid Field
Low Energy Moeller Electrons
Distance from the beam line in (cm)
0 20 40 60
80 z(cm)
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Møller Electrons in 5 Tesla Solenoid Field
Mid-Energy Moeller Electrons
Distance from the beam line in (cm)
0 20 40 60
80 z(cm)
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Møller Electrons in 5 Tesla Solenoid Field
High Energy Moeller Electrons
Møller Shield
Distance from the beam line in (cm)
0 20 40 60
80 z(cm)
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Background Situation at L1035cm-2s-1, DT 150ns
Electrons
Photons
One Event
with 5T Magnetic Field
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Background Situation at L1035cm-2s-1, DT 150ns
Electrons
Photons
Photons
One Event
One Event
Shielding
with 5 T Magnetic Field and Shielding
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Background Event Generator

• The Event generator code DINREG
• Monte Carlo nuclear fragmentation event
  generator, reproduces multiplicities and spectra
  of secondary hadrons and nuclear fragments in
  electro- and photonuclear reactions.
• Generates events fully conserving 4-momentum,
  baryon number and charge in the reaction.
• Modified to include the electroproduction
  processes in the energy range 2 - 10 GeV.
• Has been used extensively at JLab for background
  and shielding calculations.

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CLAS12 Tracking Efficiency
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CLAS12 Tracking Efficiency
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CLAS12- DC Geant Simulation
DC R3

• Geant Simulation
• CLAS12 DC geometry
• magnetic fields
• Møller shield
• Upgrade of the event
• reconstruction code

Beamline Shielding

• Luminosity Studies
• Tracking efficiency
• DC occupancy
• Resolutions
• P, q, f

Solenoid Field
DC R1
DC R2
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TORUS - Magnetic Field
CLAS12
Y(cm)
Y
Z
X (cm)
3 m
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Solenoid-Torus Magnetic Field
CLAS12
Field in TORUS sector mid-plane
T 5o
10o
15o
B(Gauss)
B(Gauss)
B(Gauss)
35o
20o
30o
B(Gauss)
B(Gauss)
B(Gauss)
Z(cm)
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CLAS12 Single Event Display
Low momentum track
5 degree angle particle
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Simulations of tracking resolutions

• Use two methods MOMRES and RECSIS12
• MOMRES is a calculation of the change to p, q and
  x due to multiple scattering at fixed locations
  and due to finite spatial resolution
• linearized approach - assumes small deviations
  from ideal
• applies to bend plane variables only
• RECSIS12 is based on the current CLAS tracking
  program, upgraded with the correct CLAS12 DC
  geometry
• Includes pattern recognition, fit of tracklets
  within single superlayers (solves left-right
  ambiguities) using timing information.
• Final track is fit globally (covariance matrix
  includes multiple scattering).
• Energy loss corrections after the global fit.

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CLAS12 Momentum Resolution
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CLAS12 Angular Resolution
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CLAS12 Drift Chambers Resolution Summary
5o

• P resolution lt 1
• q resolution lt 1mrad
• X resolution lt 200 mm

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CLAS12 Missing Mass Resolution
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Missing Mass Techniques
CLAS12
ep ? eL(pp-)X
K
K(892)
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Summary

• Drift Chamber system design parameters for the
  CLAS12 detector are well defined. They were
  developed based on
• extensive detector simulation in realistic
  background environment
• direct track reconstruction in both solenoid and
  Torus magnetic fields
• extensive simulation of the physics processes of
  the 12 GeV science program
• The current design of the Drift Chambers in
  combination of the Torus and solenoid design will
  allow us to operate CLAS12 with L 1035 cm-2s-1
  and achieve excellent resolution in p, q and f.
• With these capabilities the CLAS12 will be able
  to carry out a world-class experimental program
  in fundamental nuclear physics.

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Summary

• The magnetic configuration for the CLAS12
  Detector are well defined. They were developed
  based on
• Extensive simulation of the physics processes of
  the 12 GeV science program
• Extensive detailed design and simulation of the
  CLAS12 detectors that impact the magnet design
• Optics of the High Threshold Cerenkov Counter
• Geometry of the Forward Silicon Detector
• Geometry and design of the Polarized target
• Extensive background simulations to calculate the
  rates and radiation doses on the central
  detectors (TOF and SVT) and on the forward
  detectors (SVT, HTCC, Drift Chambers) to make
  sure of the high luminosity capabilities.