CALT-68-1148 DOE RESEARCH AND DEVELOPMENT REPORT An Experimenter’s Guide to the Helicity Formalism Jeffrey D. Richman California Institute of Techology Pasadena, California 91125 ABSTRACT The helicity formalism is developed in detail and used to obtain final state angular distributions in relativistic scattering and decay processes. The topics covered include properties of rotation operators, construction of helicity states, scattering and decay amplitudes, the parity of helicity states, and the treatment of identical particles. June, 1984 ________ Work supported in part by the U.S. Department of Energy under contract No. DE-AC03-81-ER40050.