Technicolor (physics)
The term Technicolor theories (TC) in elementary particle physics summarize extensions of the Standard Model in which the scalar Higgs boson is not a fundamental particle , but a bond state of newly introduced fermions , the Techniquarks .
The binding takes place via a likewise newly introduced strong interaction, which is structured in a similar way to quantum chromodynamics (as Yang-Mills theory , i.e. as non-Abelian gauge theory ), with new degrees of freedom of color ( colors ), hence the name Technicolor, originally based on the Technicolor as a joke -Process of the color film.
Motifs
One motive for an analogous approach in TC theories is that fundamental scalar particles such as the Higgs boson in quantum field theory are perceived by many theorists as unnatural.
Another motive is to find a fundamental theory that explains the parameters of the Standard Model ( coupling constants , mixing angles , masses).
TC theories also represent a solution to the hierarchy problem as an alternative to supersymmetric theories . This results from the mixture - through radiation corrections in 1-loop diagrams - of the very different scales of symmetry breaking ( electroweak symmetry breaking and GUT scale); this mix is inevitable in a Grand Unified Theory ("GUT").
Dynamic break of symmetry
Since Technicolor theories break the electroweak symmetry as a result of the interaction dynamics , one speaks of a theory of the dynamic symmetry breaking of the electroweak interaction .
The term “dynamic symmetry break” itself is not restricted to elementary particle physics. For example, in solid-state physics, with the BCS theory of superconductivity , with the formation of Cooper pairs from two electrons bound to one another, there is a fundamental dynamic symmetry break, albeit within the framework of an Abelian theory.
The term dynamic symmetry break was transferred to elementary particle physics in the early 1960s in the Nambu-Jona-Lasinio model (by Nambu and Jona-Lasinio ) and at the same time extended to non-Abelian physics. This theory is the model for many theories with dynamic symmetry breaking.
history
Technicolor theories were first introduced by Leonard Susskind and Steven Weinberg in the late 1970s .
Shortly thereafter, the term “Extended Technicolor” (ETC) was introduced by Savas Dimopoulos and Susskind, and by Estia Eichten and Kenneth Lane (the latter used the term Hypercolor instead of Technicolor). The aim was to integrate the calibration groups of the standard model and the TC theories into a common calibration group and thus to obtain a theory of the interaction of the usual fermions of the standard model ( leptons , quarks ) with the techniquarks (with the possibility of deriving the masses and other parameters of the Standard model).
Predictions and Problems
TC theories predict new particles that could be detected at particle accelerators like the LHC , and also provide candidates for dark matter .
However, you also encounter various difficulties, which arise, for example, from the precision measurements of the electroweak theory that are already available. In particular, ETC theories say Flavor -ändernde neutral currents ( flavor changing neutral currents , FCNCs) predicts that are suppressed in the Standard Model and for which close experimental barriers.
Walking TC theories were suggested as a way out as early as the 1980s (by Thomas Appelquist and others). They were also studied numerically in simulations of lattice scale theories in the 2000s .
Alternatives
Except TC-theories there are other theories, which also consists of fermions composite Higgs bosons included. In particular:
- Preon models, in which quarks and leptons are generally composed of even more fundamental fermions, and
- Theories of the Higgs boson as top quark - condensate (bound state of top quark and anti-top quark).
literature
- Farhi, Susskind : Technicolor . In: Physics Reports , Volume 74, 1981, p. 277 (classic review of the older TC theory)
- Kenneth Lane: Technicolor 2000 . Frascati Spring School, arxiv : hep-ph / 0007304
- Kenneth Lane: Two lectures on Technicolor . 2002, arxiv : hep-ph / 0202255
- Stephen King: Dynamical electroweak symmetry breaking . 1994, arxiv : hep-ph / 9406401
- Piai: arxiv : 1004.0176 , 2010
- Christopher Hill, Elizabeth Simmons: Strong dynamics and electroweak symmetry breaking . 2002, arxiv : hep-ph / 0203079
- Robert Shrock: Some recent results on models with dynamical electroweak symmetry breaking . 2007, arxiv : hep-ph / 0703050
Individual evidence
- ↑ According to the Anglo-American usage also Technicolor
- ^ Susskind : Dynamics of spontaneous symmetry breaking in the Weinberg-Salam theory . In: Physical Review D , Volume 20, 1979, pp. 2619-2625
- ^ Steven Weinberg Implications of dynamical symmetry breaking . In: Physical Review D , Volume 13, 1976, pp. 974-996. Weinberg Implications of dynamical symmetry breaking: An addendum . In: Physical Review D , Volume 19, 1979, pp. 1277-1280
- ^ S. Dimopoulos, L. Susskind: Mass Without Scalars . In: Nuclear Physics B , 155, 1979, pp. 237-252
- ↑ Eichten, Lane: Dynamical breaking of weak interaction symmetries . In: Physics Letters B , Volume 90, 1980, pp. 125-130
- ↑ Appelquist, Dimitra Karabali, LCR Wijewardhana: Chiral Hierarchies and Flavor-Changing Neutral Currents in Hypercolor . In: Physical Review Letters , Volume 57, 1986, pp. 957-960, abstract