CHIRAL QHD WITH VECTOR-MESONS

Quantum hadrodynamics (QHD) is the formulation of the relativistic nuclear many-body problem in terms of renormalizable quantum field theory based on hadronic degrees of freedom. A model with neutral scalar and vector mesons (sigma, omega) has had significant phenomenological success (QHD-I). An extension to include the isovector-rho through a Yang-Mills local gauge theory based on isospin, with the vector meson mass generated through the Higgs mechanism, also exists (QHD-II). Pions can be incorporated in a chiral-invariant fashion using the linear sigma model. The low-mass scalar of QHD-I is then produced dynamically through pi-pi-interactions in this chiral-invariant theory. The question arises whether one can construct a chiral-invariant QHD lagrangian that incorporates the minimal set of hadrons {N, omega, pi, rho}, where N = (p/n) is the nucleon. These are the most important degrees of freedom for describing the low-energy nucleon-nucleon interaction and nuclear structure physics. In this paper we construct a chiral-invariant Yang-Mills theory based on the local gauge symmetry SU(2)R x SU(2)L. The baryon mass is generated through spontaneous symmetry breaking (as in the linear sigma.model), and the vector meson masses are produced through the Higgs mechanism. The theory is parity conserving. Two baryon isodoublets with opposite hypercharge y are necessary to eliminate chiral anomalies. The minimal set of hadrons required consists of {N, XI; sigma, omega, pi, rho, alpha; eta, xi}, where a is the chiral partner of the rho (the alpha naturally obtains a higher mass in the model), and the eta and xi represent scalar and pseudoscalar Higgs particles. The parameters in this minimal theory consist of eight coupling constants and one mass (g(omega), g0-pi + yg1-pi, g(rho), mu(M)2, lambda(M), mu(H)2, lambda(H); m(omega)), where mu-2 and lambda define the meson interaction potentials that lead to spontaneous symmetry breaking.