A QCD sum rule description of baryon self-energies in nuclear matter

This dissertation is devoted to study of baryon self-energies in nuclear matter using the QCD sum rule method at finite density. This promising approach makes a possible connection between the relativistic nuclear physics phenomenology and the underlying theory of the strong interaction, quantum chromo-dynamics. The basic object of study is a correlator of baryon interpolating fields (made of quark fields), evaluated in the nuclear matter ground state. This correlator is calculated using both an operator product expansion and a dispersion relation with spectral ansatz. The QCD sum rules in nuclear matter relate the baryon spectral properties (such as quasibaryon self-energies) to matrix elements of QCD composite operators (condensates). Changes in baryon spectral properties relative to free space values are then related to the changes in the condensates. All density dependence of the correlator is incorporated into the in-medium condensates, which, up to dimension five, are estimated to first order in the nucleon density. At nuclear matter saturation density, the Lorentx vector self-energy for the nucleon is found to be positive with a magnitude of a few hundred MeV, which is comparable to that suggested by relativistic nuclear phenomenology. The prediction for the nucleon scalar self-energy is very sensitive to the undetermined values of the in-medium four-quark condensates.; The predicted vector self-energy for the {dollar}Lambda{dollar} hyperons is substantially smaller than the corresponding nucleon vector self-energy. The magnitude of Lorentz scalar self-energy of the {dollar}Lambda{dollar} is also smaller than the corresponding value for nucleon; however, this prediction is sensitive to the assumed density dependence of certain four-quark condensates. The implications for the {dollar}Lambda{dollar} spin-orbit force in a finite nucleus are discussed. The key phenomenological inputs are the nucleon {dollar}sigma{dollar} term, the strangeness content of the nucleon, and quark and gluon distribution functions deduced from deep-inelastic scattering experiments.