Improved Born approximation for e+e-→W+W- in the LEP200 energy region

We introduce a new representation for the one-loop corrected amplitude to e+e-→W+W-, which avoids unitarity cancellations between different invariant functions. Using this representation we demonstrate that the full one-loop amplitude can be accurately described through a Born-like structure, i.e. improved Born approximations are possible. Explicit simple improved Born approximations are given for the total and the differential cross section. For LEP200 energies these reproduce the exact one-loop results with an accuracy that is everywhere better than the expected statistical error of the experiments at LEP200. (orig.)