Projection Operator and Propagator for an Arbitrary Half-Integral Spin

Based on the solution to Bargmann-Wigner equation for an arbitrary half-integral spin, a direct derivation of the projection operator and propagator for an arbitrary half-integral spin is presented. The projection operator constructed by Behrends and Fronsdal is confirmed and simplified. The commutation rules and a general expression for the Feynman propagator for a free particle with arbitrary half-integral spin are deduced. Explicit expressions for the propagators for spins 3/2, 5/2 and 7/2 are provided.