Latifa Elouadrhiri Jefferson Lab Hall B 12 GeV Upgrade Drift Chamber Review Jefferson Lab March 6- 8, 2007 CLAS12 Drift Chambers Simulation 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 = /cm 2 /s layer occupancy < 4% Tracking efficiency>95% good acceptance at forward angles  ~ 50% at  5 o CLAS12 Drift Chambers Requirements R1 R3 R2

Background Situation at L=10 33 cm -2 s -1,  T = 150ns No Magnetic Field Drift ChambersR1 Electrons Photons

Background Situation at L=10 35 cm -2 s -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 40 o to 135 o.  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 < 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=10 35 cm -2 s -1,  T = 150ns No Magnetic Field Electrons Photons

Background Situation at L=10 35 cm -2 s -1,  T = 150ns with 5 T Magnetic Field Electrons Photons One Event

Møller Electrons in 5 Tesla Solenoid Field z(cm) Distance from the beam line in (cm) Low Energy Moeller Electrons

z(cm) Distance from the beam line in (cm) Møller Electrons in 5 Tesla Solenoid Field Mid-Energy Moeller Electrons

Møller Electrons in 5 Tesla Solenoid Field z(cm) Distance from the beam line in (cm) High Energy Moeller Electrons Møller Shield

Background Situation at L=10 35 cm -2 s -1,  T = 150ns with 5T Magnetic Field Electrons Photons One Event

Background Situation at L=10 35 cm -2 s -1,  T = 150ns with 5 T Magnetic Field and Shielding Photons One Event Electrons Photons One Event Shielding

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 GeV.  Has been used extensively at JLab for background and shielding calculations.

CLAS12 Tracking Efficiency

High tracking efficiency at L = 10 35

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 R2 DC R1 Beamline Shielding Solenoid Field

TORUS - Magnetic Field CLAS12 3 m Z Y(cm) Y X (cm)

Solenoid-Torus Magnetic Field CLAS12 Field in TORUS sector mid-plane Θ = 5 o 10 o 20 o 40 o B(Gauss) Torus Solenoid 30 o 15 o B(Gauss) Z(cm)

CLAS12 Single Event Display 5 degree angle particle Low momentum track

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 5o5o 10 o 15 o 20 o 25 o 30 o 35 o  P/P  x  m   mrad  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 ≥ cm -2 s -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.