QCD sum rules for nucleons in nuclear matter

The self-energies of quasinucleon states in nuclear matter are studied using QCD sum-rule methods. A correlator of nucleon interpolating fields, evaluated in the finite-density ground state, is calculated using both an operator product expansion and a dispersion relation with a spectral ansatz. This approach relates the nucleon spectral properties (such as the quasinucleon self-energies) to matrix elements of QCD composite operators (condensates). With increasing nucleon density, large changes in Lorentz scalar and vector self-energies arise naturally; the self-energies are found to be comparable to those suggested by relativistic nuclear physics phenomenology. The most important phenomenological inputs are the baryon density and the value of the nucleon {σ} term divided by the average current mass of the light quarks. However, the successful comparison to relativistic phenomenology is sensitive to assumptions made about the density dependence of certain four-quark condensates.