Weak currents and new quarks

Neutrino and antineutrino inelastic scattering and the implication of recent high-energy data concerning the number and the properties of quarks are reviewed. Experiments at Gargamelle together with SLAC electroproduction experiments can receive a simple interpretation in terms of a quark-parton model; therefore, low-energy data are studied by use of the two-component quark-parton model. How well it fits the data is illustrated by predictions, which are in agreement with experiments. Anomalies with respect to the low-energy description have been claimed to appear at Fermilab energies, but the experimental situation is still unclear. Two possible schemes for weak currents are discussed. The first class of models uses only left-handed charged current; it is the natural extension of the low-energy situation, where the Cabibbo current describes experimental data nicely. Variation between low energy and high energy of the quark-parton model parameters is discussed. The second class of models involves new types of currents with right-handed helicity and, consequently, new quarks with high masses. It follows that the quark-parton model formalism has to be modified in order to take into account threshold effects for heavy quark production. The slow rescaling in the Bjorken variable x implies a continuous variation with energy of these new contributions. Finally, the implications for neutral currents of the previous considerations are examined for the simplest SU(2) x U(1) gauge group. The mixing angle THETA/sub W/ is then determined; consistency with experiment is found. 8 figures, 5 tables