Fluctuations of the quark densities in nucleiG. Chanfray1 and M. Ericson1, 2
1 IPN Lyon, IN2P3-CNRS et UCB Lyon I, F69622 Villeurbanne Cedex, France
2 Theory Division, CERN, CH12111 Geneva, Switzerland
(Received: 20 July 2002 / Published online: 21 January 2003)
We study the static scalar susceptibility of the nuclear medium, i.e., the change of the quark condensate for a small modification of the quark mass. In the linear sigma model it is linked to the in-medium sigma propagator and its magnitude increases due to the mixing with the softer modes of the nucleon-hole excitations. We show that the pseudoscalar susceptibility, which is large in the vacuum, owing to the smallness of the pion mass, follows the density evolution of the quark condensate and thus decreases. At normal nuclear matter density the two susceptibilities become much closer, a partial chiral symmetry restoration effect as they become equal when the full restoration is achieved.
24.85.+p - Quarks, gluons, and QCD in nuclei and nuclear processes.
11.30.Rd - Chiral symmetries.
12.40.Yx - Hadron mass models and calculations.
21.30.-x - Nuclear forces.
© Società Italiana di Fisica, Springer-Verlag 2003