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 particles, starting with and , all denote quarks and antiquarks (factor "N" is applied). The various "V" denote the corresponding CKM matrix coefficients. Unitarity of the CKM matrix implies that Z bosons decay into a fermion and its antiparticle. As the Z boson is a mixture of the pre-symmetry-breaking W and B bosons (see weak mixing angle), each vertex factor includes a factor "T" − "Q" sin"θ" where "T" is the third component of the weak isospin of the fermion, "Q "is the electric charge of the fermion (in units of the elementary charge), and "θ" is the weak mixing