Javier Leonardo Quintanar Gonzalez Implicaciones Fısicas de la Eleccion de Fases y Base de Helicidad en las Ecuaciones de la Mecanica Cuantica Relativista. (680K, PDF) ABSTRACT. In this Work it was shown that the bispinors eigenstates imply different physical phenomena in relativistic quantum mechanics, if they are constructed with the relative phase factor introduced between 2-spinors. This fact opposes the non-relativistic theory. Thus, the pahse factor has importance. The consequences of the basis choice are also studied. The basis is understood as the linear independent system of the field functions which generate the spinor space. I choose this system in such a way that the functions are not the eigenstates of the S_z, but the eigenstates of the helicity operator. I call this basis as the helicity basis. The representations (1/2,0)+(0,1/2) and (1,0)+(0,1) are consiidered. As a result, the corresponding state functions have different behaviour with respect to the parity and the charge conjugation comparing with the usual basis.