MHV amplitudes MHV amplitudes In theoretical particle physics, maximally helicity violating amplitudes are amplitudes with n external gauge bosons, where n–2 gauge bosons have a particular helicity and the other two have the opposite helicity. These amplitudes are called MHV amplitudes, because at tree level, they violate helicity conservation to the maximum extent possible. The tree amplitudes in which all gauge bosons have the same helicity or all but one have the same helicity vanish. MHV amplitudes may be calculated very efficiently by means of the Parke–Taylor formula. Although developed for pure gluon scattering, extensions exist for massive particles, scalars (the Higgs)
Technicolor (physics) and leptons, giving them their observed masses. (In general, electroweak-eigenstate fermions are not mass eigenstates, so this process also induces the mixing matrices observed in charged-current weak interactions.) In technicolor, something else must generate the quark and lepton masses. The only natural possibility, one avoiding the introduction of elementary scalars, is to enlarge "G" to allow technifermions to couple to quarks and leptons. This coupling is induced by gauge bosons of the enlarged group. The picture, then, is that there is a large "extended technicolor" (ETC) gauge group "G" ⊃ "G" in which technifermions, quarks, and leptons live in the