S-matrix method for calculation of electromagnetic corrections to strong interactions
We develop an S-matrix method for calculating the effect of small perturbations on a partial-wave amplitude, and in particular, on the positions and residues of bound states. The method is applicable to both nonrelativistic and relativistic problems. It has, as a particular virtue, rapid convergence of the dispersion integrals. Electromagnetic corrections to strong interactions are the main application we have in mind, and modifications useful for handling the infrared divergence that occurs in this case are described in detail.
©1964 The American Physical Society. Received 27 April 1964. Work supported in part by the U.S. Atomic Energy Commission. The work reported here is included in a thesis to be submitted by Roger F. Dashen to the California Institute of Technology in partial fulfillment of the requirements for the degree of Doctor of Philosophy. [R.F.D. was a] National Science Foundation Predoctoral Fellow.