Chirally extended quantum chromodynamics

We propose a chirally extended Quantum Chromodynamics (XQCD) Lagrangian in which the fermions are coupled to elementary scalar fields through a Yukawa coupling which preserves chiral invariance. Our principle motivation is to find a new lattice formulation for QCD which avoids the source of critical slowing down usually encountered as the bare quark mass is tuned to the chiral limit. The phase diagram and the weak coupling limit for XQCD support our conjecture that the continuum limit of XQCD is in the same universality class as conventional lattice QCD. The large N solution of a toy model for XQCD is studied and here it is shown that the mass of the spurious pion and σ resonance go to infinity with the cut-off. Numerical simulations are being pursued to investigate further the possible benefits of XQCD in extracting useful QCD predictions. (orig.)