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Physicists accelerate particles up to
high energies and collide them together in order to create new particles
and study their internal structure.
Since the particle energies are so
large the correct relativistic
equations have to be used to describe the collisions. There is
an equivalence between mass and energy given by Einstein’s relation E=mc2. We can use the laws of conservation of momentum and conservation of
total energy to analyse particle collisions. The expression for the total
energy of a particle with rest mass m0 and
relativistic momentum p is;
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(1) |
Physicists also collide particles and
their antiparticles. This was the case at the Large Electron Positron
machine (LEP) at CERN; here electrons and their antiparticles, positrons,
collided together at high energies.
A positron has the same mass as an
electron but has a positive charge instead of the electron's negative
charge.
When an electron and positron collide they annihilate each other
leaving a 'blob' of energy in the form of a virtual photon. The
energy of the photon is equal to the sum of the total energies of the
electron and positron. After a very short interval of time the virtual
photon materialises into a new particle antiparticle pair.
The types of
particles that can be produced depends on the energy of the initial
collision.
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