The complete worldsheet S matrix of superstrings on AdS_3 x S^3 x T^4   with mixed three-form flux
  We determine the off-shell symmetry algebra and representations of Type IIB superstring theory on $AdS_3\times S^3 \times T^4$ with mixed R-R and NS-NS three-form flux. We use these to derive the non-perturbative worldsheet S matrix of fundamental excitations of the superstring theory. Our analysis includes both massive and massless modes and shows how turning on mixed three-form flux results in an integrable deformation of the S matrix of the pure R-R theory. 
Thomas Lloyd, Olof Ohlsson Sax, Alessandro Sfondrini, Bogdan Stefanski   Jr
hep-th