latifa elouadrhiri jefferson lab hall b 12 gev upgrade drift chamber review jefferson lab march 6-...
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Latifa ElouadrhiriLatifa ElouadrhiriJefferson LabJefferson Lab
Hall B 12 GeV Upgrade Drift Chamber Review Jefferson Lab
March 6- 8, 2007
CLAS12CLAS12 Drift Chambers Drift Chambers Simulation and Event ReconstructionSimulation and Event Reconstruction
Outline
• CLAS12 Drift Chambers Requirements • Luminosity Studies:
– Two methods: occupancy estimation, direct track reconstruction
– Results: comparison of different methods
• Resolution: p, θ, φ– Two methods: linearized calculations, track simulation and
reconstruction– Results: comparison of different methods
• Monte Carlo Simulation of Physics Reactions
Arrangement of drift chambers in CLAS12
Goals: Specifications:
measure virtual photon flux accurately
~ 1 mrad
p/p < 1%
select an exclusive reaction; e.g. only one missing pion
p < 0.05 GeV/c
p < 0.02 GeV/c
sin p < 0.02 GeV/c
measure small
cross-sections
L = 1035/cm2/s
layer occupancy < 4%
Tracking efficiency>95%
good acceptance at forward angles
~ 50% at 5o
CLAS12 Drift Chambers Requirements
R1
R3
R2
Background Situation at L=1033cm-2s-1, T = 150ns
No Magnetic Field
Drift ChambersR1Electrons
Photons
Background Situation at L=1035cm-2s-1, T = 150ns
No Magnetic Field
Electrons
Photons
Beamline equipment
CLAS12 – Single sector (exploded view)CLAS 12 Solenoid provides magnetic field for guiding Møller electrons away from detectors.
Solenoid Requirements 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 ΔB/B < 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
CLAS12 Solenoid
Solenoid Requirements
CLAS 12 Solenoid provides magnetic field for guiding Møller electrons away from detectors.
CLAS12
Background Situation at L=1035cm-2s-1, T = 150ns
No Magnetic Field
Electrons
Photons
Background Situation at L=1035cm-2s-1, T = 150ns
with 5 T Magnetic Field
Electrons
Photons
One Event
Møller Electrons in 5 Tesla Solenoid Field
0 20 40 60 80 z(cm)
Dis
tan
ce f
rom
th
e b
eam
lin
e in
(cm
)
Low Energy Moeller Electrons
0 20 40 60 80 z(cm)
Dis
tan
ce f
rom
th
e b
eam
lin
e in
(cm
)
Møller Electrons in 5 Tesla Solenoid Field Mid-Energy Moeller Electrons
Møller Electrons in 5 Tesla Solenoid Field
0 20 40 60 80 z(cm)
Dis
tan
ce f
rom
th
e b
eam
lin
e in
(cm
)
High Energy Moeller Electrons
Møller Shield
Background Situation at L=1035cm-2s-1, T = 150ns
with 5T Magnetic Field
Electrons
Photons
One Event
Background Situation at L=1035cm-2s-1, T = 150ns
with 5 T Magnetic Field and Shielding
Photons
One Event
Electrons
Photons
One Event
Shielding
Background Event GeneratorThe 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.
CLAS12 Tracking Efficiency
CLAS12 Tracking Efficiency
High tracking efficiency at L = 1035
CLAS12- DC Geant Simulation
• Geant Simulation:– CLAS12 DC geometry– magnetic fields– Møller shield
• Upgrade of the event reconstruction code
• Luminosity Studies – Tracking efficiency– DC occupancy
• Resolutions– P, ,
DC R3
DC R2DC R1
Beamline Shielding
Solenoid Field
TORUS - Magnetic FieldCLAS12
3 m
ZY
(cm
)
Y
X (cm)
Solenoid-Torus Magnetic FieldCLAS12Field in TORUS sector mid-plane
Θ = 5o
10o
20o 40o
B(G
auss
)B
(Gau
ss)
B(G
auss
)Torus
Solenoid
30o
15o
B(G
auss
)
B(G
auss
)
Z(cm)
CLAS12 Single Event Display
5 degree angle particle
Low momentumtrack
• Use two methods: “MOMRES” and “RECSIS12”
– MOMRES is a calculation of the change to p, 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 the name of the CLAS tracking program, upgraded with the correct CLAS12 DC geometry
• “clusters” found, left-right ambiguities in drift cells resolved locally, track segments from all super-layers are linked
• final track is fit globally
Simulations of tracking resolutions
CLAS12 Momentum Resolution
CLAS12 Angular Resolution
CLAS12 Drift Chambers Resolution: Summary
5o
10o
15o
20o25o
30o
35o
P/P
x
m
m
rad
Momentum Resolution Angular Resolution
Position Resolution
P resolution < 1%
resolution < 1mrad
X resolution < 200 m
CLAS12 Missing Mass Resolution
K*(892)K
CLAS12
ep → e(p-)X
Missing Mass Techniques
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, and
• With these capabilities the CLAS12 will be able to carry out a world-class experimental program in fundamental nuclear physics.
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.