Scattering in AdS2/CFT1 and the BES phase

We study worldsheet scattering for the type IIA superstring in AdS(2) x S-2 x T-6. Using the Green-Schwarz action to quartic order in fermions we take the near-BMN limit, where as in the AdS(3)/CFT2 case there are both massive and massless excitations. For the massive excitations we compute all possible tree-level processes, and show that these agree with a truncated version of the exact AdS(5) x S-5 S-matrix. We also compute several S-matrix elements involving massless excitations. At one loop we find that the dressing phase is the same Hernandes-Lopez phase appearing in AdS(5)/CFT4. We see the same phase when calculating this by semiclassical means using the PSU(1, 1 vertical bar 2)/U(1)(2) coset sigma model, for which we can also study the scattering of fermions. This supports the conjecture that the all-loop dressing phase is again the BES phase, rather than a new phase like that seen in AdS(3)/CFT2.