Cross sections and decay rates

The aim of this paper is to derive most of the results in the section headed Kinematics on pages 90-93 of the Review of Particle Properties. The authors shall keep to the notation used there as much as possible. The authors shall also derive a few other interesting results. Useful references for a lot of the material are the books of Hagedorn and Byckling and Kajantie, of De Wit and Smith and parts of the two texts of Philuhn. The authors' derivations of the standard formulae for the cross section of a 2-particle to n-particle reaction and for the lifetime of an unstable particle use ideas taken from these and other sources