QCD sum rules for ∆ isobar in nuclear matter

The self-energies of ∆ isobar propagating in nuclear matter are calculated using the finite-density QCD sum-rule methods. The calculations show that the Lorentz vector self-energy for the ∆ is significantly smaller than the nucleon vector self-energy. The magnitude of the ∆ scalar self-energy is larger than the corresponding value for the nucleon, which suggests a strong attractive net self-energy for the ∆; however, the prediction for the scalar self-energy is very sensitive to the density dependence of certain in-medium four-quark condensate. Phenomenological implications for the couplings of the ∆ to the nuclear scalar and vector fields are briefly discussed. PACS numbers: 24.85.+p, 21.65.+f, 11.55.Hx, 12.38.Lg Typeset using REVTEX