Neutrino Scattering

[Leptone]

Hey...i'm studying the reaction neutrino+antineutrino -> W(+) + W(-)
but i dont understand which are the relevant f. diagrams at first order (semiclassic approximation). Does anyone know which are???

thank you

[Bill_K]

At tree level I'd say there's just one. In the crossed channel: νe + W- → e- → νe + W-

[Parlyne]

At tree level I'd say there's just one. In the crossed channel: νe + W- → e- → νe + W-

Shouldn't there also be a contribution from an s-channel Z?