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== '''[[Higgs boson]]''' ==
== '''[[Higgs boson]]''' ==
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The '''Higgs boson''' is a massive spin-0 [[elementary particle]] in the [[Standard Model]] of [[particle physics]] that plays a key role in explaining the mass of other elementary particles. The experimental discovery of a particle consistent with the Higgs was announced in a seminar on July 4, 2012.<ref name=Higgs>
The '''Higgs boson''' is a massive spin-0 [[elementary particle]] in the [[Standard Model]] of [[particle physics]] that plays a key role in explaining the mass of other elementary particles. The experimental discovery of a particle consistent with the Higgs was announced in a seminar on July 4, 2012.<ref name=Higgs/><ref name=CERN/> This particle was first proposed by Professor [[Peter Higgs]] of [[University of Edinburgh|Edinburgh University]] in 1964 as a means to explain the origin of the masses of the elementary particles by the introduction of an fundamental scalar field. This gives all the fundamental particles mass via a process of spontaneous symmetry breaking called the ''Higgs Mechanism''. The Higgs boson was popularised as the "God particle" by the [[Nobel Prize]]-winning [[physicist]] [[Leon M. Lederman]] in his 1993 popular science book ''The God Particle: If the Universe Is the Answer, What is the Question?'' co-written with science writer Dick Teresi.<ref name=Lederman/><ref name=Fermilab/>


Announced at a CERN seminar in Geneva. See {{cite web |title=Higgs boson discovery brings scientists close to understanding mass |publisher=Washington Post |url=http://www.washingtonpost.com/business/higgs-boson-discovery-brings-scientists-lose-to-understanding-mass/2012/07/05/gJQA23iQPW_story.html |author=Thomas Mulier and Jason Gale |accessdate=2012-07-05 |quote=The data presented yesterday are the latest from the $10.5 billion [[Large Hadron Collider]], a 27-kilometer (17-mile) circumference particle accelerator buried on the border of France and Switzerland. CERN has 10,000 scientists working on the project...}}
===The Higgs mechanism===


</ref><ref name=CERN>
In the [[Standard Model]], the theory that explains experimental observations of [[elementary particle]]s, the [[Quantum chromodynamics|QCD vacuum]] has less symmetry than the force laws governing fundamental interactions. This reduced symmetry situation is not unique, and is found in many systems, among them the ground state of [[ferroelectric]]s and of [[superconductor]]s. In these systems, the greater symmetry of nature is exhibited "on average" by a mosaic of sub-domains individually with reduced symmetry, but statistically exhibiting the greater symmetry of the interactions when all the domains are viewed as an ensemble.
{{cite web |title=CERN experiments observe particle consistent with long-sought Higgs boson |date=4 July 2012 |publisher=CERN press office |accessdate=2012-07-05 |url=http://press.web.cern.ch/press/PressReleases/Releases2012/PR17.12E.html}}
</ref> This particle was first proposed by Professor [[Peter Higgs]] of [[University of Edinburgh|Edinburgh University]] in 1964 as a means to explain the origin of the masses of the elementary particles by the introduction of an fundamental scalar field. This gives all the fundamental particles mass via a process of spontaneous symmetry breaking called the ''Higgs Mechanism''. The Higgs boson was popularised as the "God particle" by the [[Nobel Prize]]-winning [[physicist]] [[Leon M. Lederman]] in his 1993 popular science book ''The God Particle: If the Universe Is the Answer, What is the Question?'' co-written with science writer Dick Teresi.<ref>Leon M. Lederman and R Teresi (1993) ''The God Particle: If the Universe Is the Answer, What is the Question?'' Dell. ISBN 0-385-31211-3</ref><ref> [http://www.newscientist.com/article/dn16618-fermilab-closing-in-on-the-god-particle.html Fermilab 'closing in' on the God particle] ''New Scientist''</ref>
 
===The Higgs Mechanism===
 
The Higgs Mechanism is vital in explaining the masses of the electroweak W and Z bosons. To understand the problem in giving mass to the vector bosons let us first consider the QED sector of the Standard Model Lagrangian.
 
::<math>\mathcal{L}_{QED} = \overline{\psi}(i \gamma^\mu\partial_\mu - m)\psi - j^\mu_{em} A_\mu - \frac{1}{4} F_{\mu\nu}F^{\mu\nu}</math>
 
Now consider how things will change if we perform a local phase rotation such that:
 
::<math>\psi(x) \rightarrow \psi'(x) = e^{i \alpha(x)} \psi(x)</math>
 
We would expect the Langrangian to remain invariant under such a rotation since to do otherwise would mean that if I chose a different phase than someone else where we could get different physics results.


In the case of superconductors, the photons, whose exchange mediates the electromagnetic interactions between [[Cooper pairs]], cannot propagate freely because of the presence everywhere of electric charge. In a similar fashion, the Higgs mechanism predicts the symmetry of electroweak interactions is broken by interactions among Higgs bosons in the vacuum, leading (among other things) to non-zero masses for the ''W<sup><big>±</big></sup>'' and ''Z'' weak bosons. In fact, the properties of mass and electric charge stem from interaction with the reduced symmetry vacuum, and are not a result of direct interactions between particles.<ref name=Tully/>


''[[Higgs boson|.... (read more)]]''
''[[Higgs boson|.... (read more)]]''

Revision as of 10:19, 6 July 2012

Higgs boson

The Higgs boson is a massive spin-0 elementary particle in the Standard Model of particle physics that plays a key role in explaining the mass of other elementary particles. The experimental discovery of a particle consistent with the Higgs was announced in a seminar on July 4, 2012.[1][2] This particle was first proposed by Professor Peter Higgs of Edinburgh University in 1964 as a means to explain the origin of the masses of the elementary particles by the introduction of an fundamental scalar field. This gives all the fundamental particles mass via a process of spontaneous symmetry breaking called the Higgs Mechanism. The Higgs boson was popularised as the "God particle" by the Nobel Prize-winning physicist Leon M. Lederman in his 1993 popular science book The God Particle: If the Universe Is the Answer, What is the Question? co-written with science writer Dick Teresi.[3][4]

The Higgs mechanism

In the Standard Model, the theory that explains experimental observations of elementary particles, the QCD vacuum has less symmetry than the force laws governing fundamental interactions. This reduced symmetry situation is not unique, and is found in many systems, among them the ground state of ferroelectrics and of superconductors. In these systems, the greater symmetry of nature is exhibited "on average" by a mosaic of sub-domains individually with reduced symmetry, but statistically exhibiting the greater symmetry of the interactions when all the domains are viewed as an ensemble.

In the case of superconductors, the photons, whose exchange mediates the electromagnetic interactions between Cooper pairs, cannot propagate freely because of the presence everywhere of electric charge. In a similar fashion, the Higgs mechanism predicts the symmetry of electroweak interactions is broken by interactions among Higgs bosons in the vacuum, leading (among other things) to non-zero masses for the W± and Z weak bosons. In fact, the properties of mass and electric charge stem from interaction with the reduced symmetry vacuum, and are not a result of direct interactions between particles.[5]

.... (read more)

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