Scalar mesons and glueballs in a chiral U(3) x U(3) quark model with 't Hooft interaction

In a U(3) x U(3) quark chiral model of the Nambu-Jona-Lasinio (NLJ) type with the 't Hooft interaction, the ground scalar isoscalar mesons and a scalar glueball are described. The glueball (dilaton) is introduced into the effective meson Lagrangian written in a chirally symmetric form on the base of scale invariance. The singlet-octet mixing of scalar isoscalar mesons and their mixing with the glueball are taken into account. Mass spectra of the scalar mesons and glueball and their strong decays are described. (authors)