Nambu's Nobel Prize, the 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 σ meson is the mediating particle. Though already introduced in 1957 by Schwinger, the σ 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 σ 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.

On the hadron mass decomposition

“…More generally, the energy in a given reference frame determined by the time-like unit four-vector u μ is given by p · u. For the rest frame, we simply have 1 Note that in the light-front form of dynamics, boost invariance is sometimes incorrectly called frame independence. 2 Sometimes people consider that physical quantities have to be Lorentz invariant, and so they conclude that decompositions are often unphysical and hence uninteresting or irrelevant.…”

“…The current light quark masses obtained from such a mechanism correspond however to only about 1% of the nucleon mass. Therefore, the mass of the ordinary matter around us essentially finds its origin in the strong interactions which confine quarks and gluons inside hadrons, and not the BEH mechanism [1,2].…”

Contribution ofσmeson exchange to elastic lepton-proton scattering

“…These models give us various estimations of the coupling of σ to the proton. In our calculations, we choose to follow the predictions of models [10] and [22]. The former approach uses the effective hadron Lagrangian in the quark model to calculate σN N coupling.…”

“…We do not fix a value of the decay width Γ σ→γγ , but instead use a range obtained in the partial wave amplitudes analysis [24] Γ σ→γγ = 1.8 ÷ 2.3 keV (m σ = 500 MeV) as well as the range obtained in the Compton scattering analysis [10] Γ σ→γγ = 2.3 ÷ 2.9 keV (m σ = 666 MeV).…”

The Origin of the Nucleon Mass

“…While the Brout-Englert-Higgs mechanism generates the current quark masses, it accounts only for about 2% of the nucleon mass. The remaining 98% comes from the relativistic kinetic energy and the strong interactions confining quarks and gluons inside hadrons [1,2], described by quantum chromodynamics (QCD).…”