204 research outputs found
Nucleon Sigma Term and In-medium Quark Condensate in the Modified Quark-Meson Coupling Model
We evaluate the nucleon sigma term and in-medium quark condensate in the
modified quark-meson coupling model which features a density-dependent bag
constant. We obtain a nucleon sigma term consistent with its empirical value,
which requires a significant reduction of the bag constant in the nuclear
medium similar to those found in the previous works. The resulting in-medium
quark condensate at low densities agrees well with the model independent linear
order result. At higher densities, the magnitude of the in-medium quark
condensate tends to increase, indicating no tendency toward chiral symmetry
restoration.Comment: 9 pages, modified version to be publishe
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-1/2 and spin-3/2 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. These new sum
rules are analyzed along with previous spin-1/2 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 GeV and
GeV at nuclear matter saturation density.Comment: 10 page RevTeX Manuscript with embedded figures. Revised manuscript
accepted for publication. This and related papers may also be obtained from
http://www.phys.washington.edu/~derek/Publications.htm
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