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ZEUS

ZEUS-Gruppenbild.gif (125678 bytes)
Members of the ZEUS group in front of the detector

The ZEUS detector has dimensions of 12 m x 10 m x 19 m,   and Its total weight is 3600 tons.  It is staffed by han 450 physicists from 12 countries, making it a truly international scientific collaboration.

Click on various parts of the image below to show what pieces of the detector do.

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fwd_btn.gif (616 bytes)Click for events in ZEUS

Central Tracking Detector (CTD),
   FTD and RTD

The Central Tracking Detector, and the Rear and Front Tracking Detectors,  are used to measure the paths of charged particles from HERA's high energy collisions.  The detector lies within a magnetic field which bends the paths of charged particles.  Particles with a large momentum travel in almost straight paths, while very low momentum particles bend to make tight spirals.  The tracking chamber contains many fine wires, with some at different angles to each other, and the chamber is filled with a gas.  When a charged particle passes through the gas it ionizes the gas along the path it follows. The electrons emitted from the ionized gas drift in the chamber towards the wires, where they produce a signal.  This allows the position of the particle to be calculated accurately.
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Electromagnetic Calorimeter (EMC or ECAL)

The name "calorimeter" normally refers to a device that measures heat. Particle physicists however use this term for any device that is used to measure the energy of a particle.  It achieves this by absorbing all the energy of the particle, and releasing a shower of low energy particles.   By evaluating the number of particles produced in the shower the energy of the the original particle can be deduced.  The EM calorimeter is designed to stop particles such as electrons and photons. Hadrons (particles made from quarks) are relatively unhindered by this section of the calorimeter,  and pass through leaving only a small trace of energy. The calorimeter is made from layers of uranium and scintillator.

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Hadrons Calorimeter (HAC or HCAL)

The hadron calorimeter works in a similar way to the EMC but is much thicker so as to absorb all the hadron energy.
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Muon chamber

Beyond all the other detectors are the muon chambers.  Most particles will have been stopped by now by the other sections of the detector.  Muons are the only charged particles to reach this far, so it is only here that they reveal their identity. 
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