Cracking the Particle Code of the Universe by Moffat John W

Author:Moffat, John W.
Language: eng
Format: epub, mobi, pdf
Publisher: Oxford University Press, USA
Published: 2014-09-27T04:00:00+00:00

TECHNICOLOR

In solid-state physics, the explanation of how superconductivity works lies in having pairs of electrons (Cooper pairs) binding and condensing together at very low temperatures in metals. In the standard model of particle physics as proposed by Weinberg and Salam, the Higgs boson is considered an elementary scalar particle, not a composite of other particles. But what if the Higgs is a composite of other particles, like the Cooper pair condensates in superconductivity? In 1976, Steven Weinberg,3 followed by Leonard Susskind in 1979,4 and Savas Dimopoulos and Susskind also in 1979,5 proposed another way of solving the weak-interaction problem of lack of renormalizability and unitarity. They called their solution “Technicolor.” What they proposed was that we replicate the quark-theory QCD at a higher energy with new particles, called Technicolor particles because they would carry the quark characteristic called color. (Recall that hadrons are observed to be colorless because they are composite particles containing quarks, with three colors that combine, or cancel out, to form a white or colorless hadron.) According to this theory, the Higgs boson is a composite of these Technicolor particles. In the original models, these physicists were concerned only with predicting the masses of the W and Z bosons.

Some versions of Technicolor do not have a Higgs boson at all. Instead of proposing an elementary Higgs boson to explain electroweak phenomena, the Technicolor models “hide” the electroweak symmetry and generate the W and Z boson masses through the dynamics of new, postulated gauge interactions. These new gauge interactions were made invisible at lower energies to fit the experimental data from low energies that do not, so far, reveal these interactions.

The early versions of Technicolor were extended so that one could predict the masses of the quarks and leptons. However, these models ran into trouble in that they predicted neutral current flavor changing in decays of Technicolor particles that violated experimental data. Bob Holdom then proposed a way of avoiding these problems by introducing a type of fine-tuning called walking Technicolor.

A notable feature of the Technicolor theory is that the interactions of the Technicolor particles are intrinsically strong interactions, not weak. Although the Technicolor model is a copy of the lower-energy QCD, new strong forces have to be postulated to bind the Technicolor particles together. Therefore, the perturbation methods of quantum field theory used in the standard electroweak model or in QED and in high-energy QCD cannot be used. In low-energy QCD, when it is necessary to explain the confinement of quarks in hadrons, perturbative methods of calculation can fail, and ill-understood nonperturbative methods have to be used, with a large QCD coupling constant.

We do not understand how to perform calculations in which the coupling strength of the interactions is large. The coupling strength of QED, of photons and electrons, is determined by the fine-structure constant, alpha, which is approximately 1 divided by 137, and therefore a small number compared with unity. This small coupling strength of photons and electrons allows us to do the perturbation calculations such

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