W -boson pair production at lepton colliders in the Feynman-diagram gauge

We calculate helicity amplitudes for <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:msup><a:mi>e</a:mi><a:mo>−</a:mo></a:msup><a:msup><a:mi>e</a:mi><a:mo>+</a:mo></a:msup><a:mo stretchy="false">→</a:mo><a:msup><a:mi>W</a:mi><a:mo>−</a:mo></a:msup><a:msup><a:mi>W</a:mi><a:mo>+</a:mo></a:msup></a:math> analytically in the Feynman-diagram (FD) gauge. We show that, unlike in the unitary gauge, there is no energy growth of the individual Feynman amplitudes for the longitudinally polarized bosons, and the contributions from the associated Goldstone bosons are manifest even without taking the high-energy limit. We also find that the physical distributions can be interpreted by the individual amplitudes in the FD gauge.