The Vector Meson Form Factor Analysis in Light-Front Dynamics

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We study the form factors of vector mesons using a covariant fermion field theory model in (3+1) dimensions. Performing a light-front 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.