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ZEUS Central Tracking Detector (CTD) PowerPoint PPT Presentation

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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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ZEUSCentral Tracking Detector (CTD)

How does it work?

How is it used?

Mark Bell


HERA accelerator:

6km long

920GeV protons &

27.5GeV electrons



ZEUS Physics: Deep inelastic scattering, structure functions, electroweak,

heavy flavours, exotics, QCD, diffraction.

Understanding proton & photon structure.

ZEUS Detector

A multipurpose detector




Weighs 3600 tonnes = 1000 elephants

Why does ZEUS need a CTD?

Charged particle detection

Reconstruct final state by:

Identifying tracks and vertices

Measuring momentum

Measuring dE/dx

Trigger information

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

CTD design


9 superlayers

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

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

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.

CTD uses




Particle ID

First level trigger




Second level trigger

FADC timing

Track parameters

High pt tracks

Example event

ZEUS Run 45923

Event 1349

Neutral current

High pt electron

Hadron jet

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!

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