New QCD sum rules for nucleons in nuclear matter

Two new QCD sum rules for nucleons in nuclear matter are obtained from a mixed correlator of spin-12 and spin-32 interpolating fields. These new sum rules, which are insensitive to the poorly known four-quark condensates, provide additional information on the nucleon scalar self-energy. They are analyzed along with previous spin-12 interpolator-based sum rules which are also insensitive to the poorly known four-quark condensates. The analysis indicates consistency with the expectations of relativistic nuclear phenomenology at nuclear matter saturation density. However, a weaker density dependence near saturation is suggested. Using previous estimates of in-medium condensate uncertainties, we find M∗ = 0.64−0.09+0.13 GeV and Συ = 0.29−0.10+0.06 GeV at nuclear matter saturation density.