Particle spectrum of Poincare gauge theory is investigated in detail, in particular paticle' s mass and energy. Besides usual graviton, the torsion field gives rise to massive 2+, 2-, 1 +, 1-, o+ and oparticles, each of which obeys the Klein-Gordon equation. We find that there are at most three normal particles, defined by having positive mass and positive energy: namely, only nine possible triplets, (2+, 1+, o-), (2+, 1-, o-), (2+, o+, o-) and their parity conjugate, and (1 +, o+, o-) and its

more »

... arity conjugate and finally (1 +, 1·, o-). Further reduction to two and one particles is also possible provided z+ and zcannot coexist. Conditions of nine parameters, a, /3, r, a" a" ···, aa, for these normal particles to exist are also obtained. The fundamental fields are then the linearized gravitational field h1w and the contorsion field K,lfv· The former part, though modified by the presence of the torsion field, gives rise to the usual graviton which is massless and spinvarity is given by 2'. The latter part yields six massive particles of 2', 2 , 1 , 1-, 0' and o-. Tt is, however. not known that these particles are normal; that is, particles obey the Klein-Gordon equation, having positive mass and positive energy. In III only the first point that these particles satisfy the Klein-Gordon equation was insured.