Applications of QCD sum-rule methods to the physics of nuclei are reviewed, with an emphasis on calculations of baryon self-energies in infinite nuclear matter. The sum-rule approach relates spectral properties of hadrons propagating in the finite-density medium, such as optical potentials for quasinucleons, to matrix elements of QCD composite operators (condensates). The vacuum formalism for QCD sum rules is generalized to finite density, and the strategy and implementation of the approach is discussed. Predictions for baryon self-energies are compared to those suggested by relativistic nuclear physics phenomenology. Sum rules for vector mesons in dense nuclear matter are also considered.

We introduce twist-two quark interference fragmentation functions in helicity density matrix formalism and study their physical implications. We show how the nucleon's transversity distribution can be probed through the final state interaction between two mesons (π + π − , KK, or πK) produced in the current fragmentation region in deep inelastic scattering on a transversely polarized nucleon.

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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

QCD sum rules for vector mesons (ρ, ω, φ) in nuclear matter are reexamined with an emphasis on the reliability of various sum rules. Monitoring the continuum contribution and the convergence of the operator product expansion plays crucial role in determining the validity of a sum rule. The uncertainties arising from less than precise knowledge of the condensate values and other input parameters are analyzed via a Monte-Carlo error analysis. Our analysis leaves no doubt that vector-meson masses decrease with increasing density. This resolves the current debate over the behavior of the vector-meson masses and the sum rules to be used in extracting vector meson properties in nuclear matter. We find a ratio of ρ-meson masses of m ρ * /m ρ = 0.78± 0.08 at nuclear matter saturation density. *