Pentaquark, cusp and rescattering in single kaon photoproduction off   deuterium
  In very well defined part of the phase space, $K N$ and $\Lambda N$ rescattering depend on on-shell elementary matrix elements and on the low momentum components of the deuteron wave function. This provides us with the unique opportunity to study details in the scattering amplitudes that may have escaped the analysis of reactions induced on a nucleon target by Kaon and Hyperon beams at low energies. When folded with a typical experimental mass resolution, a narrow state with a width of 1 MeV would contribute by no more than 10% to the $KN$ mass spectrum. On the contrary, a cusp would be easily detected near the $\Sigma$ production threshold in the $\Lambda N$ mass spectrum. 
J.M. Laget