Saga of the Composite Models - A perspective for LHC

Aula B. Touschek (Laboratori Nazionali di Frascati, Via Enrico Fermi 40, Frascati)

Aula B. Touschek

Laboratori Nazionali di Frascati, Via Enrico Fermi 40, Frascati

Via Enrico Fermi 40 00044 Frascati

The last revolution of the particle physics leading to the Standard Model was triggered by the Fermi-Yang/Sakata model before the advent of the quark model. Now facing the pre-revolutionary era of LHC which is expected to reveal the Origin of Mass, I will first review the Nambu-Jona-Lasinio (NJL) model as a composite model for the Origin of Mass of the nucleon, elementary particle then, which is a prototype of the composite Higgs boson, such as the top quark condensate. The dynamical mass generation a la NJL (NJL mechanism, or dynamical symmetry breaking) turned out to be actually realized in QCD, a gauge theory for the composite hadrons, where however the Origin of Mass is more sophisticated than that of the NJL model which was converted from a built-in mass scale inherent to the dimensionful four-fermion coupling introduced by hand. The Origin of Mass in QCD on the other hand is originated from the intrinsic scale which does not exist in the classical theory but arises purely from the quantum effects called scale anomaly. We then argue the composite Higgs model in the gauge theory, particularly the technicolor model, which is analogous to QCD in the sense that the mass scale comes from the scale anomaly. A crucial difference from QCD is required, however, as to the NJL mechanism to convert the intrinsic mass scale into the particle masses: Approximate scale (conformal) symmetry due to almost non-running coupling constant is the essential ingredient, which leads to a large anomalous dimension near unity in sharp contrast to QCD which has a vanishing anomalous dimension due to the asymptotically-free running (inverse-logarithmically damping) coupling constant. A remnant of the scale symmetry would be the dilaton in technicolor, pseudo Nambu-Goldstone boson of the scale symmetry, what we called techni-dilaton. This is the composite Higgs boson in the near scale-invarinat technicolor to be observed at LHC. Lattice studies on such a near scale-invariant gauge dynamics are becoming urgent. Composite gauge bosons will also be touched upon, base on the hidden local symmetry in connection to the higher dimensional gauge theory or holographic gauge theory where excited composite states W'/Z' or techni-rho/omega mesons, etc. may be regarded as the Kaluza-Klein modes.

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