Dynamical symmetry breaking and the sigma-meson mass in quantum chromodynamics

The spontaneous breakdown of chiral symmetry is analyzed dynamically via bound-state Bethe-Salpeter equations. While in general spontaneous mass generation is linked to a massless 0−$0-$ pion and no specific constraint on a massive 0+$0+$ meson, for the particular theory of asymptotically free QCD it is shown that a 0+$0+$ σ$\sigma$ meson should exist with mass mσ≈600 to 700$m_{\sigma }\approx 600 \mathrm{to} 700$ MeV.