Kaon photoproduction operator for use in nuclear physics

Using diagrammatic techniques we have obtained a new operator for the process p(γ,${\mathrm{K}}^{+}$)${\mathrm{\Lambda }}^0$ which includes the Born terms in addition to resonances in the s and u channel near threshold. The coupling constants are obtained by a least squares fit to cross section and polarization data for photon energies from threshold through 1400 MeV. We find a number of changes from the earlier operator obtained by Thom about twenty years ago when less data were available. To aid in comparing this operator to other work, we give its multipole decomposition in the center of mass frame, and to aid in its use in nuclear physics we write out the operator in a frame fixed in the nucleus and, further, take the nonrelativistic limit of the operator as Blomqvist and Laget did for the pion photoproduction case. Finally, we discuss the validity of the nonrelativistic limit of this operator.