ABSTRACT
The first indication that the atom contains a point-like nucleus came from experiments of Rutherford. He scattered alpha particles from a gold foil. Since the negative charges were known to be much lighter than the alpha particles, they would not scatter the alpha particles very much. If the positive charges inside the atom were more or less uniformly distributed, the alpha particles would not be scattered through wide angles. Rutherford found to the contrary that the alpha particles were scattered by wide angles. A particle that can take part in the strong interactions is called a ‘hadron’. There are two kinds of hadrons: those of half-integer angular momentum are called ‘baryons’ and those of integer angular momentum are the ‘mesons’. The hadrons are composed of more elementary constituents: the quarks, anti-quarks and gluons. These constituents are collectively called partons. Quantum Chromodynamics is the fundamental theory of strong interactions.
