Nambu's Nobel Prize, the sigma meson and the mass of visible matter

Abstract

The electroweak Higgs boson has been discovered in ongoing experiments at the LHC, leading to a mass of this particle of 126 GeV. This Higgs boson mediates the generation of mass for elementary particles, including the mass of elementary (current) quarks. These current-quark masses leave 98% of the mass of the atom unexplained. This large fraction is mediated by strong interaction, where instead of the Higgs boson the sigma meson is the mediating particle. Though already introduced in 1957 by Schwinger, the s meson has been integrated out in many theories of hadron properties because it had not been observed and was doubted to exist. With the observation of the s meson in recent experiments on Compton scattering by the nucleon at MAMI (Mainz) it has become timely to review the status of experimental and theoretical researches on this topic.