2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/179452The transition amplitude is obtained for a free massive particle of arbitrary spin by calculating the path integral in the index-spinor formulation within the BFV-BRST approach. None renormalizations of the path integral measure were applied. The calculation has given the Weinberg propagator written in the index-free form with the use of index spinor. The choice of boundary conditions on the index spinor determines holomorphic or antiholomorphic representation for the canonical description of particle/antiparticle spin.31 pages, Latex, version published in Class. Quantum GravHigh Energy Physics - Theorytext