Boris L. Ioffe

Chiral effective theory of strong interactions

A review of chiral effective theory (CET) is presented. CET is based on quantum chromodynamics (QCD) and describes strong interaction processes at low energies. It is proved that CET arises as a consequence of the spontaneous violation of chiral symmetry in QCD — the appearance of chiral-symmetry-violating vacuum condensates. The Goldstone theorem is proved for the case of QCD, and the existence of the octet of massless Goldstone bosons (π, K, η) is demonstrated in the limit of massless u, d and s quarks (or the existence of the triplet of massless pions in the limit mu, md → 0). It is shown that the same phenomenon — the appearance of quark condensate in QCD — which is responsible for the Goldstone bosons also gives rise to chiral-symmetry-violating massive baryons. The general form of the CET Lagrangian is derived. Examples of higher order corrections to tree diagrams in CET are considered. The Wess–Zumino term (i.e., the p4 term in the CET Lagrangian) is given. Low energy sum rules are presented. QCD and CET at finite temperature are discussed. In the CET framework, the T2 correction to quark condensate in QCD is calculated at finite temperature, and results including higher order temperature corrections are presented. These results indicate on a phase transition to occur at T ≈ 150–200 MeV in QCD. The mixing of current correlators in order of T2 is proved.

The origin of mass and experiments on future high-energy accelerators

The observable world is the one consisting of nucleons and electrons. The mass of the nucleon arises from chiral symmetry breaking in quantum chromodynamics (QCD), so that high-energy accelerator experiments cannot give any clues to the nature of the mass of matter in the observable world. The origin of the mass of matter will be clarified when the mechanism of chiral symmetry breaking in QCD will be established.