This event shows the result of the annihilation of an electron and positron into a quark - antiquark pair. However, as quarks interact so strongly, they are never seen on their own; they transform some of the energy of the electron - positron annihilation into more quark - antiquark pairs, then combine in threes to produce particles such as protons and neutrons or in quark-antiquark pairs. It is the tracks of these particles that are recorded in the detector.
The two jets are coloured red and green in this event. The lines represent the tracks of the charged particles; they curve in the magnetic field produced by the solenoid which surrounds the electromagnetic calorimeter (shown in white). The blocks represent energy deposited in the calorimeters.
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