An. Ivanov et Ni. Troitskaya, PI-MESON AND A(1)-MESON PHYSICS IN CURRENT-ALGEBRA AT THE QUARK LEVEL, Nuovo cimento della Società Italiana di Fisica. A. Nuclei, particles and fields, 108(5), 1995, pp. 555-563
The a(1)-->pi(pi pi) S-wave decay and the low-energy pi pi-scattering
are considered within current algebra at the quark level (CA)(q) and c
hiral perturbation theory at the quark level (CHPT)(q) based on the ex
tended Nambu-Jona-Lasinio model with linear realization of chiral U(3)
x U(3) symmetry. It is shown that low-energy interactions of a new ki
nd, produced by convergent constituent-quark diagrams and being very u
seful for the theoretical understanding of experimental data on the pr
ocesses under consideration, are very good blending with (CA)(q) and (
CHPT)(q). The contribution of these interactions is caused by the appl
ication of ordinary rules of quantum field theory. These interactions
allow one to escape the problem of the quark condensate, vanishing in
the chiral limit.