  We consider the worldsheet S matrix of superstrings on an AdS3xS3xT4 NS-NS
background in uniform light-cone gauge. We argue that scattering is given by a
CDD factor that is non-trivial only between opposite-chirality particles,
yielding a spin-chain-like Bethe Ansatz. Our proposal reproduces the spectrum
of non-protected states computed from the Wess-Zumino-Witten description and
the perturbative tree-level S matrix. This suggests that the model is an
integrable deformation of a free theory similar to those arising from the
T-Tbar composite operator.
