W3 string scattering

Abstract The group theoretic method is extended to include fields with a background charge. This formalism is used to compute the tree level scattering for W 3 strings. The scattering amplitudes involve Ising model correlation functions. A detailed study of the four-tachyon amplitude shows that the W 3 string must possess additional states in its spectrum associated with intercept 1 2 and the energy operator of the Ising model.