2 00 3 Dynamically Spontaneous Symmetry Breaking and Masses of Lightest Nonet Scalar Mesons as Composite Higgs Bosons

Based on the (approximate) chiral symmetry of QCD Lagrangian and bound state assumption of effective meson fields due to strong interactions of gluons, a nonlinearly realized effective chiral Lagrangian for meson fields is resulted from integrating over the quark fields by using the new finite regularization method. As the new method preserves the symmetry principles of the original theory and meanwhile keeps the finite quadratic term given by a physically meaningful characteristic energy scale M c , it then leads the effective chiral field theory to have a dynamically spontaneous symmetry breaking mechanism. The gap equations are yielded as the minimal conditions of the effective potential in the effective theory. The instanton effects are included via the induced interactions discovered by 't Hooft and found to play an important role in obtaining the physical solutions for the gap equations. The lightest nonet scalar mesons (σ, f 0 , a 0 and κ) appearing as the chiral partners of the nonet pseudoscalar mesons are found to be as the composite Higgs bosons with masses below the characteristic energy scale M c ∼ 1.2 GeV. In particular, the mass of the singlet scalar (or the σ) is found to be m σ ≃ 688 MeV.