The vector meson form factor analysis in light-front dynamics

We study the form factors of vector mesons using a covariant fermion field theory model in 3 + 1 dimensions. Performing a light-front (LF) calculation in the q⁺ = 0 frame in parallel with a manifestly covariant calculation, we note the existence of a nonvanishing zero-mode contribution to the light-front current J⁺ and find a way of avoiding the zero mode in the form factor calculations. Upon choosing the light-front gauge (∈_h=±⁺ = 0) with circular polarization and with spin projection h = ↑ ↓ = ±, only the helicity zero-to-zero matrix element of the plus current receives zero-mode contributions. Therefore, one can obtain the exact light-front solution of the form factors using only the valence contribution if only the helicity components, (h' h) = (+ +), (+ -), and (+ 0), are used. We also compare our results obtained from the light-front gauge in the light-front helicity basis (i.e. h = ±,0) with those obtained from the non-LF gauge in the instant form linear polarization basis (i.e. h=x,y,z) where the zero-mode contributions to the form factors are unavoidable.