EPJ

2024 Impact factor 2.8
EPJ A - Hadrons and Nuclei
Hadrons and Nuclei
Eur. Phys. J. A 4, 171-186

Self-consistent treatment of the quark condensate and
hadrons in nuclear matter

E.G. Drukarev - M.G. Ryskin - V.A. Sadovnikova

St. Petersburg Nuclear Physics Institute, 188350 Gatchina, Russia

Received: 8 October 1998 Communicated by V.V. Anisovich

Abstract
We calculate the contribution of pions to the $\bar qq$-expectation value $\kappa(\rho)= \langle M\vert\bar qq\vert M\rangle$ in symmetric nuclear matter. We employ exact pion propagator renormalized by nucleon-hole and isobar-hole excitations. Conventional straightforward calculation leads to the ``pion condensation" at unrealistically small values of densities, causing even earlier restoration of chiral symmetry. This requires a self-consistent approach, consisting in using the models, which include direct dependence of in-medium mass values on $\kappa(\rho)$, e.g. the Nambu-Jona-Lasinio-model. We show, that in the self-consistent approach the $\rho$-dependence of the condensate is described by a smooth curve. The ``pion condensate" point is removed to much higher values of density. The chiral restoration does not take place at least while $\rho<2.8\rho_0$ with $\rho_0$ being the saturation value. Validity of our approach is limited by possible accumulation of heavier baryons (delta isobars) in the ground state of nuclear matter. For the value of effective nucleon mass at the saturation density we found $m^*(\rho_0)=0.6m$, consistent with nowadays results of other authors.

PACS
13.75.Gx Pion-baryon interactions - 24.80.+y Nuclear tests of fundamental interactions and symmetries - 24.85.+p Quarks, gluons, and QCD in nuclei and nuclear processes

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