Study of the KL to PI+PI-GAMMA Direct Emission Vertex

We have perfomed studies of the KL to PI+PI-GAMMA Direct Emission (DE) and Inner Bremsstrahlung (IB) vertices, based on data collected by KTeV during the 1996 Fermilab fixed target run. We find a1/a2 = -0.737 +- 0.034 GeV^2 for the DE form-factor parameter in the rho-propagator parametrization, and report on fits of the form-factor to linear and quadratic functions as well. We concurrently measure B.R.(KL to PI+PI-GAMMA, E_gamma >20 MeV)/(KL to PI+PI-) = (20.8 +- 0.3)*10^-3, and a KL to PI+PI-GAMMA DE/(DE + IB) branching ratio of 0.683 +- 0.011.