Experimental tests of quantum chromodynamics

Experimental results from deep inelastic lepton—nucleon scattering, from electron - positron annihilation to hadrons and from massive lepton - pair production in hadron collisions, are discussed. The data obtained so far give qualitative support for Q C D . Serious quantitative comparisons are beset with difficulties, which arise first because of discrepancies between different experiments, and secondly because in addition to the perturbative effects that have been calculated theoretically, there are non-perturbative contributions for which there are no reliable estimates. These appear to be important in the momentum transfer range that can be investigated experimentally at present.