Structure of scalar mesons and the Higgs sector of strong interaction

Abstract

The scalar mesons sigma(600), kappa(800), f(0)(980) and a(0)(980) together with the pseudo Goldstone bosons pi, K and eta may be considered as the Higgs sector of strong interaction. After a long time of uncertainty about the internal structure of the scalar mesons there now seems to be consistency which is in line with the major parts of experimental observations. Great progress has been made by introducing the unified model of Close and Tornqvist. This model states that scalar mesons below 1 GeV may be understood as q(2)(q) over bar (2) in S-wave with some q (q) over bar in P-wave in the center, further out they rearrange as (q (q) over bar)(2) and finally as meson-meson states. The P-wave component inherent in the structure of the neutral scalar mesons can be understood as a doorway state for the formation of the scalar meson via two-photon fusion, whereas in nucleon Compton scattering these P-wave components serve as intermediate states. The masses of the scalar mesons are predicted in terms of spontaneous and explicit symmetry breaking.