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ZEUS Central Tracking Detector (CTD)

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,

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ZEUS Central Tracking Detector (CTD)

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  1. ZEUSCentral Tracking Detector (CTD) How does it work? How is it used? Mark Bell

  2. ZEUS on HERA at DESY HERA accelerator: 6km long 920GeV protons & 27.5GeV electrons HERA ZEUS ZEUS Physics: Deep inelastic scattering, structure functions, electroweak, heavy flavours, exotics, QCD, diffraction. Understanding proton & photon structure.

  3. ZEUS Detector A multipurpose detector CTD 12m 19m Weighs 3600 tonnes = 1000 elephants

  4. Why does ZEUS need a CTD? Charged particle detection Reconstruct final state by: Identifying tracks and vertices Measuring momentum Measuring dE/dx Trigger information

  5. What properties must the CTD have? CTD specifications 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

  6. CTD design 2.05m 9 superlayers 600 drift cells 5000 sense wires 20000 field wires Covers polar angle from 15º to 164º 0.79m 1.4T magnetic field along beam axis provided by superconducting solenoid coil

  7. Gas Mixture 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

  8. CTD drift cell Ground wire Shaper wire Sense wire Field wire Spatial resolution ~ 0.1mm Field, ground and shaper wires provide uniform field. Cell rotated to compensate for Lorentz angle.

  9. CTD uses Tracks Momentum dE/dx Particle ID First level trigger Z-by-timing Tracks Vertex Second level trigger FADC timing Track parameters High pt tracks

  10. Example event ZEUS Run 45923 Event 1349 Neutral current High pt electron Hadron jet Identified by CTD

  11. Summary 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!

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