Year: 2013
Type: article
Abstract: The structure of the electromagnetic vertex function of spin-$3/2$ particles is analyzed in a general way, for the diagonal and off-diagonal couplings, of charged as well as neutral particles including the case of self-conjugate (Majorana) particles. The restrictions imposed by common principles such as electromagnetic gauge invariance and Hermiticity are studied, and the implications due to the discrete space-time symmetries or the Majorana condition are deduced when they are applicable. In some cases certain features of the vertex function are analogous to the known ones for the spin-$1/2$ or spin-1 particles, but we find and discuss other particular properties which are related to the spin-$3/2$ Rarita--Schwinger representation. For example, in the diagonal Majorana case, the vertex function can contain a term of the form ${\ensuremath{\gamma}}_{\ensuremath{\mu}}{\ensuremath{\gamma}}_{5}$, which resembles the axial charge radius term for Majorana neutrinos, plus another one that resembles the vertex function for self-conjugate spin-1 particles, but with the particularity that the two terms may not appear independently of each other, but instead with a specific relative coefficient. In essence this is due to the requirement that the vertex function does not mix the genuine spin-$3/2$ degrees of freedom with the spurious spin-$1/2$ components of the Rarita--Schwinger representation. The analogous results for the other cases (off-diagonal and charged couplings) are discussed as well.
Author: José F. Nieves
Institution: University of Puerto Rico at Río Piedras
Language: Latvian
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2073275975