Understanding Neutron Beta Decay: The Role of W Boson and Energies Involved

[chis]

Most accepted theories make sense, but the energies involved in the beta decay of a neutron into a proton confuses me.
How can a down quark change into an up quark by emiting an electron and an anti electron neutrino via a w boson, the figures don't add up!
Using the figures of mass it goes like this:

Neutron 939ish Mev
Down Quark 4.8 Mev

Wboson 80Gev

Electron .511 Mev
Electron Neutrino 2.2 ev

Up Quark 2.4 Mev

Proton 938 Mev

My question is - Where does the Wboson Get so much energy from?

Thanks
Chris

 

[Meir Achuz]

The W boson is virtual, so its effective mass is given by E^2-p^2, where E and p come from conservation of 4-momentum. This is not the W rest mass.