Perpustakaan Digital ITB

Spin-3/2 particle theory is still an unclear subject since its first formulation by W. Rarita and J. Schwinger in 1941. The problems are about extra degree of freedom for describing spin-3/2 particles and the lack of relativistic property of wave solutions when interaction with external (electromagnetic) field is introduced (known as Velo-Zwanziger problem). In this thesis we consider Rarita-Schwinger (RS) formalism as a standard description of spin-3/2 particle which widely used for the delta (1232) baryon resonance. Also, we discuss a new approach by Napsuciale-Kirchbach (NK) based on the squared Pauli-Lubanski (PL) eigen equation to describe the spin-3/2 field. Then we do a test of gauge invariance of the theories by performing gauge transformation of polarization vector in the corresponding Compton scattering amplitude. We find that both theories are gauge invariant in their full propagators and vertices. Since NK formalism is free from Velo-Zwanziger problem, it seems that this theory could be a better description of spin-3/2 particle after some experimental verifications.