In-medium chiral condensate beyond linear density approximation

Journal Article · Fri Feb 15 00:00:00 EST 2008 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.77.025204· OSTI ID:21068152

Kaiser, N; Homont, P de; Weise, W ^[1]

---

1. Physik Department, Technische Universitaet Muenchen, D-85747 Garching (Germany)

In-medium chiral perturbation theory is used to calculate the density dependence of the quark condensate <qq>. The corrections beyond the linear density approximation are obtained by differentiating the interaction contributions to the energy per particle of isospin-symmetric nuclear matter with respect to the pion mass. Our calculation treats systematically the effects from one-pion exchange (with m{sub {pi}}-dependent vertex corrections), iterated 1{pi}-exchange, and irreducible 2{pi}-exchange including intermediate {delta}(1232)-isobar excitations, with Pauli-blocking corrections up to three-loop order. We find a strong and nonlinear dependence of the ''dropping'' in-medium condensate on the actual value of the pion (or light quark) mass. In the chiral limit, m{sub {pi}}=0, chiral restoration appears to be reached already at about 1.5 times normal nuclear matter density. By contrast, for the physical pion mass, m{sub {pi}}=135 MeV, the in-medium condensate stabilizes at about 60% of its vacuum value above that same density. Effects from 2{pi}-exchange with virtual {delta}(1232)-isobar excitations turn out to be crucial in generating such pronounced deviations from the linear density approximation above {rho}{sub 0}. The hindered tendency toward chiral symmetry restoration provides a justification for using pions and nucleons as effective low-energy degrees of freedom at least up to twice nuclear matter density.

• OSTI ID: 21068152
• Journal Information: Physical Review. C, Nuclear Physics, Vol. 77, Issue 2; Other Information: DOI: 10.1103/PhysRevC.77.025204; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
APPROXIMATIONS
CHIRAL SYMMETRY
CHIRALITY
CORRECTIONS
D QUARKS
DEGREES OF FREEDOM
DELTA-1232 BARYONS
DENSITY
EXCITATION
ISOSPIN
MEV RANGE
NONLINEAR PROBLEMS
NUCLEAR MATTER
NUCLEONS
PERTURBATION THEORY
PIONS
QUARK CONDENSATION
QUARK-QUARK INTERACTIONS
REST MASS
U QUARKS