Aim: to identify different charged particle antiparticle pairs, by studying their trajectories in a magnetic field.

You are now looking at a circular cross-sectional view through the point where the collisions took place in the LEP accelerator at CERN. The incident electron and positron beams travelled along the axis of the accelerator, i.e. into and out-of the screen; they met and annihilated in the centre of this view. In the real accelerator the area represented by the screen covered several square metres.

The animation displays charged particle-antiparticle
pairs produced at the centre at various energies. Their trajectories (dashed lines) are curved by the uniform magnetic field (B) applied along the beam axis, i.e. coming out-of the screen towards you!

The computer selects, at random, from four charged particle antiparticle pairs, shown below with their rest masses: