2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/51945We study the theory of the Lorentz group (1/2,0)+(0,1/2) representation in the helicity basis of the corresponding 4-spinors. As Berestetski, Lifshitz and Pitaevskii mentioned, the helicity eigenstates are not the parity eigenstates. Relations with the Gelfand-Tsetlin-Sokolik-type quantum field theory are discussed. Finally, a new form of the parity operator (which commutes with the Hamiltonian) is proposed in the Fock space.In Spanish. Misprints correctedHigh Energy Physics - Theorytext