Nonvanishing zero modes in the light-front current

We find that the zero mode (q{sup +}=0 mode of a continuum theory) contribution is crucial to obtaining the correct values of the light-front current J{sup {minus}} in the Drell-Yan (q{sup +}=0) frame. In the exactly solvable model of (1+1)-dimensional scalar field theory interacting with gauge fields, we quantify the zero-mode contribution and observe that the zero-mode effects are very large for the light meson form factors even though they are substantially reduced for the heavy meson cases. {copyright} {ital 1998} {ital The American Physical Society}