ZEUS Central Tracking Detector (CTD). How does it work? How is it used?. Mark Bell. ZEUS on HERA at DESY. HERA accelerator: 6km long 920GeV protons & 27.5GeV electrons. HERA. ZEUS. ZEUS Physics: Deep inelastic scattering, structure functions, electroweak,
How does it work?
How is it used?
920GeV protons &
ZEUS Physics: Deep inelastic scattering, structure functions, electroweak,
heavy flavours, exotics, QCD, diffraction.
Understanding proton & photon structure.
A multipurpose detector
Weighs 3600 tonnes = 1000 elephants
Charged particle detection
Reconstruct final state by:
Identifying tracks and vertices
Good spatial and momentum resolution
Wide angular acceptance
Short drift time
Solution: Jet drift chamber in uniform magnetic field
Small individual cells
Separates close together tracks
Provides fast information for trigger
600 drift cells
5000 sense wires
20000 field wires
Covers polar angle from
15º to 164º
1.4T magnetic field along beam axis provided by superconducting solenoid coil
Ar:CO2:C2H6 in respective proportions 83:12:5.
Argon: Noble gas – good gain at low voltage, stable
High specific ionisation, and cheaper than Kr and Xe
CO2: Reduces electron drift velocity
Stops whisker growth on wires
Ethane: Polyatomic molecule – quencher
Enables CTD to operate at a higher voltage
Spatial resolution ~ 0.1mm
Field, ground and shaper wires provide uniform field.
Cell rotated to compensate for Lorentz angle.
First level trigger
Second level trigger
High pt tracks
ZEUS Run 45923
High pt electron
Identified by CTD
How does the CTD work?
Jet drift chamber (working reliably since 1992)
Specific gas mixture
Small cells with lots of wires
Uniform electric and magnetic fields
What is the CTD used for?
Particle identification and triggering
Allows interesting physics to be done!