Lorentz-invariant phase-space integrals for decay and production processes involving $n$ particles in the final state—with integrand containing arbitrary invariant functions of momenta of particles—are transformed into simple definite integrals over Mandelstam-like variables. Given the $T$-matrix element squared as a function of scalar products of initial- and final-state particle momenta, the results may be used for the computation of the production cross section, decay rate, energy and momentum spectra, invariant mass spectra, and angular correlations.

• Received 16 September 1968

DOI:https://doi.org/10.1103/PhysRev.185.1865