Amplitude for N -Gluon Superstring Scattering

We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope α^'. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in α^', for the so-called maximally helicity violating configurations, with $N=4$, 5 and $N=6$. We also obtain the leading O(α^'2) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.