Editing Standard Model (section)

=== Higgs boson ===
{{Main|Higgs boson}}

The Higgs particle is a massive [[Scalar field theory|scalar]] elementary particle theorized by [[Peter Higgs]] ([[1964 PRL symmetry breaking papers|and others]]) in 1964, when he showed that Goldstone's 1962 theorem (generic continuous symmetry, which is spontaneously broken) provides a third polarisation of a massive vector field. Hence, Goldstone's original scalar doublet, the massive spin-zero particle, was [[1964 PRL symmetry breaking papers|proposed as the Higgs boson]], and is a key building block in the Standard Model.<ref>
{{cite journal
 |author=G.S. Guralnik
 |year=2009
 |title=The History of the Guralnik, Hagen and Kibble development of the Theory of Spontaneous Symmetry Breaking and Gauge Particles
 |journal=[[International Journal of Modern Physics A]]
 |volume=24 |issue=14 |pages=2601–2627
 |arxiv=0907.3466
 |bibcode=2009IJMPA..24.2601G
 |doi=10.1142/S0217751X09045431
 |s2cid=16298371
}}</ref> It has no intrinsic [[Spin (physics)|spin]], and for that reason is classified as a [[boson]] with spin-0.<ref name=":0" />

The Higgs boson plays a unique role in the Standard Model, by explaining why the other elementary particles, except the [[photon]] and [[gluon]], are massive. In particular, the Higgs boson explains why the photon has no mass, while the [[W and Z bosons]] are very heavy. Elementary-particle masses and the differences between [[electromagnetism]] (mediated by the photon) and the [[weak force]] (mediated by the W and Z bosons) are critical to many aspects of the structure of microscopic (and hence macroscopic) matter. In [[electroweak interaction|electroweak theory]], the Higgs boson generates the masses of the leptons (electron, muon, and tau) and quarks.  As the Higgs boson is massive, it must interact with itself.

Because the Higgs boson is a very massive particle and also decays almost immediately when created, only a very high-energy [[particle accelerator]] can observe and record it. Experiments to confirm and determine the nature of the Higgs boson using the [[Large Hadron Collider]] (LHC) at [[CERN]] began in early 2010 and were performed at [[Fermilab]]'s [[Tevatron]] until its closure in late 2011. Mathematical consistency of the Standard Model requires that any mechanism capable of generating the masses of elementary particles must become visible{{clarify|reason=Isn't "apparent" or "manifest" needed here instead of "visible"?|date=July 2013}} at energies above {{val|1.4|ul=TeV}};<ref>
{{cite journal
 |author1=B.W. Lee |author2=C. Quigg |author3=H.B. Thacker |year=1977
 |title=Weak interactions at very high energies: The role of the Higgs-boson mass
 |journal=[[Physical Review D]]
 |volume=16 |issue=5 |pages=1519–1531
 |bibcode=1977PhRvD..16.1519L
 |doi=10.1103/PhysRevD.16.1519
}}</ref> therefore, the LHC (designed to collide two {{val|7|u=TeV}} proton beams) was built to answer the question of whether the Higgs boson actually exists.<ref>
{{cite news
 |date=11 November 2009
 |title=Huge $10 billion collider resumes hunt for 'God particle'
 |url=http://www.cnn.com/2009/TECH/11/11/lhc.large.hadron.collider.beam/index.html
 |publisher=CNN
 |access-date=2010-05-04
}}</ref>

On 4 July 2012, two of the experiments at the LHC ([[ATLAS experiment|ATLAS]] and [[Compact Muon Solenoid|CMS]]) both reported independently that they had found a new particle with a mass of about {{val|125|ul=GeV/c2}} (about 133 proton masses, on the order of {{val|e=-25|u=kg}}), which is "consistent with the Higgs boson".<ref>
{{cite web
 |date=4 July 2012
 |title=Observation of a New Particle with a Mass of 125&nbsp;GeV
 |url=http://cms.web.cern.ch/news/observation-new-particle-mass-125-gev
 |publisher=CERN
 |access-date=2012-07-05
}}</ref><ref name="NYT-20120704">
{{cite news
 |author=D. Overbye
 |date=4 July 2012
 |title=A New Particle Could Be Physics' Holy Grail
 |url=https://www.nytimes.com/2012/07/05/science/cern-physicists-may-have-discovered-higgs-boson-particle.html
 |newspaper=The New York Times
 |access-date=2012-07-04
}}</ref> On 13 March 2013, it was confirmed to be the searched-for Higgs boson.<ref name="CERN_20130314">
{{cite web
 |url=https://home.cern/news/press-release/cern/new-results-indicate-particle-discovered-cern-higgs-boson
 |title=New results indicate that particle discovered at CERN is a Higgs boson
 |date=14 March 2013
 |publisher=CERN
 |access-date=2020-06-14
}}</ref><ref name="CERN_EPS2017">
{{cite web
 |url=https://press.cern/update/2017/07/lhc-experiments-delve-deeper-precision
 |title=LHC experiments delve deeper into precision
 |date=11 July 2017
 |publisher=CERN
 |access-date=2017-07-23
 |archive-date=14 July 2017
 |archive-url=https://web.archive.org/web/20170714090456/http://press.cern/update/2017/07/lhc-experiments-delve-deeper-precision
 |url-status=dead
}}</ref>