Strange Baryonic Matter from Chiral Effective Lagrangians

Abstract

We investigate the existence of bound states of baryons in a kaon condensate using chiral mean field theory. The interactions are described by an effective SU(3)_L X SU(3)_R chiral lagrangian where terms of higher order in density, baryon momentum, and kaon mass are suppressed by powers of the symmetry breaking scale, Lambda. We take up to next to leading order terms (n = 2,3,4). We search for infinite baryon number solutions, namely ``strange baryonic matter&#39;&#39;, using a Thomas-Fermi approximation for a slowly varying condensate and a lowest order Hartree approximation to describe the many body interactions. For simplicity we study a pure K^0 condensate and only neutrons, the lightest baryons in that condensate. We find solutions with neutron number densities, rho_n > 3.5 rho_0, where rho_0 is the infinite nuclear matter density. This is consistent with the estimate of the onset of a K-condensate at rho_n = 2-4 rho_0. We show that the binding energies, E_b, grow with rho_n and for rho_n < 7 rho_0 (at rho_n > 7 rho_0 perturbative expansion is lost) we find E_b < 150 MeV (E_b < 70 MeV for rho_n < 5 rho_0) even in the most favorable cases. These binding energies may be too low for this type of matter to appear and persist in the early universe.