Alternatives to the Standard Higgs Model

{{See also|Introduction to the Higgs field}}

In particle physics, elementary particles and forces give rise to the world around us. Physicists explain the behaviors of these particles and how they interact using the Standard Model—a widely accepted framework believed to explain most of the world we see around us.Heath, Nick, [http://www.techrepublic.com/blog/european-technology/the-cern-tech-that-helped-track-down-the-god-particle/815?tag=nl.e101/ The Cern tech that helped track down the God particle], TechRepublic, July 4, 2012 Initially, when these models were being developed and tested, it seemed that the mathematics behind those models, which were satisfactory in areas already tested, would also forbid elementary particles from having any mass, which showed clearly that these initial models were incomplete. In 1964 three groups of physicists almost simultaneously released papers describing how masses could be given to these particles, using approaches known as symmetry breaking. This approach allowed the particles to obtain a mass, without breaking other parts of particle physics theory that were already believed reasonably correct. This idea became known as the Higgs mechanism, and later experiments{{which|date=February 2016}} confirmed that such a mechanism does exist—but they could not show exactly how it happens.

The simplest theory for how this effect takes place in nature, and the theory that became incorporated into the Standard Model, was that if one or more of a particular kind of "field" (known as a Higgs field) happened to permeate space, and if it could interact with elementary particles in a particular way, then this would give rise to a Higgs mechanism in nature. In the basic Standard Model there is one field and one related Higgs boson; in some extensions to the Standard Model there are multiple fields and multiple Higgs bosons.

In the years since the Higgs field and boson were proposed as a way to explain the origins of symmetry breaking, several alternatives have been proposed that suggest how a symmetry breaking mechanism could occur without requiring a Higgs field to exist. Models which do not include a Higgs field or a Higgs boson are known as Higgsless models. In these models, strongly interacting dynamics rather than an additional (Higgs) field produce the non-zero vacuum expectation value that breaks electroweak symmetry.

A partial list of proposed alternatives to a Higgs field as a source for symmetry breaking includes:

• Technicolor models break electroweak symmetry through new gauge interactions, which were originally modeled on quantum chromodynamics.{{Citation | author=Steven Weinberg | title=Implications of dynamical symmetry breaking | journal=Physical Review D | volume=13 | date=1976 | pages=974–996 | doi=10.1103/PhysRevD.13.974 | postscript=.|bibcode = 1976PhRvD..13..974W | issue=4 }}
  {{Citation | author=S. Weinberg | title=Implications of dynamical symmetry breaking: An addendum | journal=Physical Review D | volume=19 | date=1979 | pages=1277–1280 | doi=10.1103/PhysRevD.19.1277 | postscript=.|bibcode = 1979PhRvD..19.1277W | issue=4 }}{{Citation | author=Leonard Susskind | s2cid=17294645 | title=Dynamics of spontaneous symmetry breaking in the Weinberg-Salam theory | journal=Physical Review D| volume=20 | date=1979 | pages=2619–2625 | doi=10.1103/PhysRevD.20.2619 | postscript=.|bibcode = 1979PhRvD..20.2619S | issue=10 | osti=1446928 }}
• Extra-dimensional Higgsless models use the fifth component of the gauge fields to play the role of the Higgs fields. It is possible to produce electroweak symmetry breaking by imposing certain boundary conditions on the extra dimensional fields, increasing the unitarity breakdown scale up to the energy scale of the extra dimension.{{citation |first1=C. |last1=Csaki |first2=C. |last2=Grojean |first3=L. |last3=Pilo |first4=J. |last4=Terning |date=2004|title=Towards a realistic model of Higgsless electroweak symmetry breaking |journal=Physical Review Letters |volume=92 |issue=10 |pages=101802 |doi=10.1103/PhysRevLett.92.101802 |pmid=15089195 |arxiv=hep-ph/0308038 |bibcode=2004PhRvL..92j1802C|s2cid=6521798 }}{{citation |first1=C. |last1=Csaki |first2=C. |last2=Grojean |first3=L. |last3=Pilo |first4=J. |last4=Terning |date=2004 |title=Gauge theories on an interval: Unitarity without a Higgs |journal=Physical Review D |volume=69 |issue=5 |pages=055006 |doi=10.1103/PhysRevD.69.055006 |last5=Terning |first5=John |arxiv=hep-ph/0305237|bibcode = 2004PhRvD..69e5006C |s2cid=119094852 }} Through the AdS/QCD correspondence this model can be related to technicolor models and to "UnHiggs" models in which the Higgs field is of unparticle nature.{{Citation |first1=X. |last1=Calmet |first2=N. G. |last2=Deshpande |first3=X. G. |last3=He |first4=S. D. H. |last4=Hsu |year=2009 |title=Invisible Higgs boson, continuous mass fields and unHiggs mechanism |doi=10.1103/PhysRevD.79.055021 |journal=Physical Review D |volume=79 |issue=5 |pages=055021 |arxiv=0810.2155|bibcode = 2009PhRvD..79e5021C |s2cid=14450925 |url=http://ntur.lib.ntu.edu.tw//bitstream/246246/164074/1/94.pdf }}
• Models of composite W and Z vector bosons.{{citation |first1=L. F. |last1=Abbott |first2=E. |last2=Farhi |date=1981 |title=Are the Weak Interactions Strong? |journal=Physics Letters B |volume=101 |issue=1–2 |pages=69 |doi=10.1016/0370-2693(81)90492-5 |bibcode = 1981PhLB..101...69A |url=https://cds.cern.ch/record/134137/files/198102095.pdf }}{{citation |first=Neil Alexander |last=Speirs |date=1985 |title=Composite models of weak gauge bosons|type=PhD Thesis |publisher=Durham University}}
• Top quark condensate.
• "Unitary Weyl gauge". By adding a suitable gravitational term to the standard model action in curved spacetime, the theory develops a local conformal (Weyl) invariance. The conformal gauge is fixed by choosing a reference mass scale based on the gravitational coupling constant. This approach generates the masses for the vector bosons and matter fields similar to the Higgs mechanism without traditional spontaneous symmetry breaking.{{citation |first1=M. |last1=Pawlowski |first2=R. |last2=Raczka |date=1994 |title=A Unified Conformal Model for Fundamental Interactions without Dynamical Higgs Field |doi=10.1007/BF02148570 |journal=Foundations of Physics |volume=24 |issue=9 |pages=1305–1327 |arxiv=hep-th/9407137|bibcode = 1994FoPh...24.1305P |s2cid=17358627 }}
• Asymptotically safe weak interactions{{Citation |first=X. |last=Calmet |date=2011 |title=Asymptotically safe weak interactions|journal=Mod. Phys. Lett. A|volume=26|issue=21 |pages=1571–1576 |arxiv=1012.5529|bibcode = 2011MPLA...26.1571C |doi = 10.1142/S0217732311035900 |s2cid=118712775 }}{{Citation |first=X. |last=Calmet |date=2011 |title=An Alternative view on the electroweak interactions|journal=Int. J. Mod. Phys. A|volume=26|issue=17 |pages=2855–2864 |arxiv=1008.3780|bibcode = 2011IJMPA..26.2855C |doi = 10.1142/S0217751X11053699 |s2cid=118422223 }} based on some nonlinear sigma models.{{Citation |first1=A. |last1=Codello |first2=R. |last2=Percacci |year=2009 |title=Fixed Points of Nonlinear Sigma Models in d>2 |doi=10.1016/j.physletb.2009.01.032 |journal=Physics Letters B |volume=672 |issue=3 |pages=280–283 |arxiv=0810.0715|bibcode = 2009PhLB..672..280C |s2cid=119223124 }}
• Preon and models inspired by preons such as Ribbon model of Standard Model particles by Sundance Bilson-Thompson, based in braid theory and compatible with loop quantum gravity and similar theories.{{Citation |last1=Bilson-Thompson |first1=Sundance O. |last2=Markopoulou |first2=Fotini |last3=Smolin |first3=Lee |title=Quantum gravity and the standard model |date=2007 |journal=Class. Quantum Grav. |volume=24 |issue=16 |pages=3975–3993 |doi=10.1088/0264-9381/24/16/002 |postscript=. |arxiv=hep-th/0603022|bibcode = 2007CQGra..24.3975B |s2cid=37406474 }} This model not only explains mass{{Clarify|reason=What does "explain mass" mean? For instance, are the experimental values predicted?|date=March 2012}} but leads to an interpretation of electric charge as a topological quantity (twists carried on the individual ribbons) and colour charge as modes of twisting.
• Symmetry breaking driven by non-equilibrium dynamics of quantum fields above the electroweak scale.{{Citation|doi=10.1209/0295-5075/82/11001|title=Bifurcations and pattern formation in particle physics: An introductory study|journal=EPL|volume=82|issue=1|pages=11001|date=2008|last1=Goldfain|first1=E.|bibcode=2008EL.....8211001G|s2cid=62823832 }}{{Citation

|last=Goldfain

|date=2010

|title=Non-equilibrium Dynamics as Source of Asymmetries in High Energy Physics

|url=http://www.ejtp.com/articles/ejtpv7i24p219.pdf

|journal=Electronic Journal of Theoretical Physics

|volume=7

|issue=24

|pages=219

|access-date=2011-07-27

|archive-date=2022-01-20

|archive-url=https://web.archive.org/web/20220120174017/http://www.ejtp.com/articles/ejtpv7i24p219.pdf

|url-status=dead

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• Unparticle physics and the unhiggs.{{Citation|arxiv=0807.3961|last1=Stancato|first1=David|title=The Unhiggs|journal=Journal of High Energy Physics|volume=2009|issue=11|pages=101|last2=Terning|first2=John|year=2009|doi=10.1088/1126-6708/2009/11/101|bibcode = 2009JHEP...11..101S |s2cid=17512330}}{{Citation|arxiv=0901.3777|last1=Falkowski|first1=Adam|title=Electroweak Precision Observables and the Unhiggs|journal=Journal of High Energy Physics|volume=2009|issue=12|pages=061|last2=Perez-Victoria|first2=Manuel|date=2009|doi=10.1088/1126-6708/2009/12/061|bibcode = 2009JHEP...12..061F |s2cid=17570408}} These are models that posit that the Higgs sector and Higgs boson are scaling invariant, also known as unparticle physics.
• In theory of superfluid vacuum masses of elementary particles can arise as a result of interaction with the physical vacuum, similarly to the gap generation mechanism in superconductors.{{Citation|arxiv=0912.4139|last1= Zloshchastiev|first1= Konstantin G.|title= Spontaneous symmetry breaking and mass generation as built-in phenomena in logarithmic nonlinear quantum theory|journal= Acta Physica Polonica B|volume= 42|issue= 2|pages= 261–292|year= 2011|doi= 10.5506/APhysPolB.42.261|bibcode = 2011AcPPB..42..261Z |s2cid= 118152708}}{{Citation|arxiv=1108.0847|last1= Avdeenkov|first1= Alexander V.|title= Quantum Bose liquids with logarithmic nonlinearity: Self-sustainability and emergence of spatial extent|journal= Journal of Physics B: Atomic, Molecular and Optical Physics|volume= 44|issue= 19|pages= 195303|last2= Zloshchastiev|first2= Konstantin G.|date= 2011|doi= 10.1088/0953-4075/44/19/195303|bibcode = 2011JPhB...44s5303A |s2cid= 119248001}}
• UV-completion by classicalization, in which the unitarization of the WW scattering happens by creation of classical configurations.{{Citation|arxiv=1010.1415 |title=UV-Completion by Classicalization |journal=Journal of High Energy Physics |volume=2011 |issue=8 |pages=108 |first1=Gia |last1=Dvali |first2=Gian F. |last2=Giudice |first3=Cesar |last3=Gomez |first4=Alex |last4=Kehagias |date=2011 |bibcode = 2011JHEP...08..108D |doi = 10.1007/JHEP08(2011)108 |s2cid=53315861 }}

• Composite Higgs models

{{Reflist|30em}}

• [http://xstructure.inr.ac.ru/x-bin/theme3.py?level=1&index1=271624 Higgsless model on arxiv.org]

Category:Physics beyond the Standard Model

Category:Electroweak theory

Category:Mass