Exploring the time-like region for the elastic form factor in the light-front quantization

Even though the Drell-Yan-West formulation is the most rigorous and well-es tablished framework to compute the exclusive processes, its utility has bee n limited only to the space-like region because of the intrinsic kinematic constraint q(+) = 0. We present an explicit example demonstrating how one m ay obtain the necessary information (i.e. nonvalence or so called Z-graph c ontribution) in the timelike region of exclusive process without encounteri ng a formidable task of direct calculation that has hindered so far the pro gress in this area. In the analysis of q (Q) over bar bound state form fact ors using an exactly solvable model of (3 + 1)-dimensional scalar field the ory interacting with gauge fields, the results analytically continued from the space-like region coincide exactly with the direct results in the time- like region. This example verifies that the method of analytic continuation is capable of yielding the effect of complicate nonvalence contributions. The meson peaks analogous to the vector meson dominance (VMD) phenomena are also generated at the usual VMD positions. 0 2001 Elsevier Science B.V. Al l rights reserved.