The bound state S-matrix for image superstring Original Research Article

We determine the S-matrix that describes scattering of arbitrary bound states in the light-cone string theory in image. The corresponding construction relies on the Yangian symmetry and the superspace formalism for the bound state representations. The basic analytic structure supporting the S-matrix entries turns out to be the hypergeometric function image. We show that for particular bound state numbers it reproduces all the scattering matrices previously obtained in the literature. Our findings should be relevant for the TBA and Lüscher approaches to the finite-size spectral problem. They also shed some light on the construction of the universal R-matrix for the centrally-extended image superalgebra.