The charge response of a meson-correlated relativistic Fermi gas

The quasielastic longitudinal electromagnetic response function RL is studied within the context of the relativistic Fermi gas model extending our previous investigations, which only included pionic correlations and currents. Four mesons are now employed (π, ρ, σ and ω, via the Bonn potential) and the many-body dynamics are extended to the full antisymmetrized random-phase approximation built upon a Hartree-Fock basis. Wherever possible the Lorentz covariance of the problem is respected. The first three energy-weighted moments of the reduced response are computed, namely, the zeroth moment (Coulomb sum rule), the first moment (related to the position of the quasielastic peak) and the second moment (related to the peak width or variance). We discuss a procedure to be used in fixing the value of the only free parameter characterizing the model, namely the Fermi momentum kF, which is being related, rather than to the average nuclear density, to the half-width of the quasielastic response. (orig.)