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)
W′ and Z′ bosons W′ and Z′ bosons In particle physics, W′ and Z′ bosons (or W-prime and Z-prime bosons) refer to hypothetical gauge bosons that arise from extensions of the electroweak symmetry of the Standard Model. They are named in analogy with the Standard Model W and Z bosons. W′ bosons often arise in models with an extra SU(2) gauge group. is spontaneously broken to the diagonal subgroup SU(2) which corresponds to the electroweak SU(2). More generally, we might have "n" copies of SU(2), which are then broken down to a diagonal SU(2). This gives rise to "n"−1 W′, W′ and Z′ bosons.