Dynamical vertex mass generation and chiral symmetry breaking on the light front

Naively, helicity flip amplitudes for fermions seem to vanish in the chiral limit of light-front QCD, which would make it nearly impossible to generate a small pion mass in this framework. Using a simple model, it is illustrated how a large helicity flip amplitude is generated dynamically by summing over an infinite number of Fock space components. While the kinetic mass is basically generated by a zero-mode induced counter-term, the vertex mass is generated dynamically by infinitesimally small, but nonzero, moments. Implications for the renormalization of light-front Hamiltonians for fermions are discussed. [S0556-2821(98)07421-9].