2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/218727The relativistic approach to electroweak properties of two-particle composite systems developed in Ref. [A.F.Krutov, V.E.Troitsky, Phys.Rev.C. 65 (2002) 045501] is generalized here to the case of nonzero spin. In developed technique the parametrization of matrix elements of electroweak current operators in terms of form factors is a realization of the Wigner--Eckart theorem on the Poincaré group and form factors are reduced matrix elements. The $ρ$ meson charge form factor is calculated as an example.4 pages, 1 figureHigh Energy Physics - Phenomenologytext