QCD sum rules for nucleons in nuclear matter III

Abstract

The self-energies of quasinucleon states in nuclear matter are investigated using a finite-density /CD sum-rule approach developed previously. The sum rules are obtained for a general /CD interpolating field for the nucleon. The key phenomenological inputs are the nucleon 0 term, the strangeness content of the nucleon, and quark and gluon distribution functions deduced from deepinelastic scattering. The emphasis is on testing the sensitivity and stability of sum-rule predictions to variations of the condensates and other input parameters. At nuclear matter saturation density, the Lorentz vector self-energy is found to be positive with a magnitude of a few hundred MeV, which is comparable to that suggested by relativistic nuclear phenomenology. This result is quite stable. The prediction for the scalar self-energy is very sensitive to the undetermined values of the in-medium four-quark condensates.PACS number(s): 24.85. +p, 21.65.+f, 11. 55.Hx, 12.38.Lg

Relativistic nuclear model with point-couplings constrained by QCD and chiral symmetry

“…We proceed now with a central theme of our work: establishing connections between the density-dependent point couplings in (10)(11)(12)(13)(14)(15) and constraints from QCD. Two key features of low-energy, non perturbative QCD are at the origin of this discussion: the presence of a non-trivial vacuum characterized by strong condensates and the important role of pionic fluctuations governing the low-energy, long wavelength dynamics according to the rules imposed by spontaneously broken chiral symmetry.…”

“…In-medium QCD sum rules relate the changes of the scalar quark condensate and the quark density at finite baryon density, with the scalar and vector self-energies of a nucleon in the nuclear medium. In leading order which should be valid at densities below and around saturated nuclear matter, the condensate part of the scalar self-energy is expressed in terms of the density dependent chiral condensate as follows [11,12,13]:…”

“…Even though the presence of large scalar and vector potentials cannot be directly verified experimentally, there is strong evidence, in particular from nuclear matter saturation and spinorbit splittings in finite nuclei, that the magnitude of each of these potentials is of the order of several hundred MeV in the nuclear interior. Studies based on finite-density QCD sum rules have shown how such large scalar and vector nucleon self-energies arise naturally from in-medium changes of the scalar quark condensate and the quark density [11,12,13]. In applications of QHD models to finite nuclei, however, the scalar and vector nucleon self-energies are treated in a purely phenomenological way.…”

New QCD sum rules for nucleons in nuclear matter

“…In-medium factorization expresses these chirally-even operators in terms of the square of a chirallyodd operator whose density dependence is likely to be very different. As such, the density dependence of these problematic four-quark operators is generally unknown [3,5,6].…”

“…The QCD sum-rule approach [1] is a particularly useful method for connecting the properties of QCD to observed nuclear phenomena [2][3][4][5][6][7][8][9][10]. Recent progress in understanding the origin of the large and canceling isoscalar Lorentz-scalar and -vector self-energies for propagating nucleons in nuclear matter has been made via the analysis of QCD sum rules generalized to finite nucleon density [2][3][4][5][6].…”