Conformal techniques, bosonization and tree-level string amplitudes

Calculational tools are provided allowing the determination of tree-level amplitudes for processes involving fermions and bosons in heterotic and superstring theories. A simple representation is given of the cocycle operators that are needed for bosonization of conformal operators, including spin fields and ghosts. This permits explicit computation of all correlation functions. The general m-boson, 2 n-fermion tree-level scattering amplitude in the open superstring is derived and a typical calculation of a four-point amplitude in the o(16)xo(16) heterotic string is presented in manifestly Lorentz-covariant form. An analysis of the branch-cut singularities in the o(16)xo(16) model is performed. In addition, the covariant form of the 'new formalism' is developed. Particular attention is given to a lattice viewpoint of these results. (orig.)