Editing Elementary particle (section)

{{Short description|Subatomic particle having no substructure}}
{{Standard model of particle physics}}

In [[particle physics]], an '''elementary particle''' or '''fundamental particle''' is a [[<!-- wiktionary:particle| -->subatomic particle]] that is not composed of other particles.<ref name=PFI /> The [[Standard Model]] presently recognizes seventeen distinct particles—twelve [[fermion]]s and five [[boson]]s. As a consequence of [[Flavour (particle physics)|flavor]] and [[Quantum chromodynamics|color]] combinations and [[antimatter]], the fermions and bosons are known to have 48 and 13 variations, respectively.<ref name="braibant">{{cite book |last1=Braibant |first1=S. |url=https://books.google.com/books?id=0Pp-f0G9_9sC&q=61+fundamental+particles&pg=PA314 |title=Particles and Fundamental Interactions: An Introduction to Particle Physics |last2=Giacomelli |first2=G. |last3=Spurio |first3=M. |publisher=[[Springer Science+Business Media|Springer]] |year=2009 |isbn=978-94-007-2463-1 |pages=313–314 |access-date=19 October 2020 |archive-url=https://web.archive.org/web/20210415025723/https://books.google.com/books?id=0Pp-f0G9_9sC&q=61+fundamental+particles&pg=PA314 |archive-date=15 April 2021 |url-status=live}}</ref> Among the 61 elementary particles embraced by the Standard Model number: [[electron]]s and other [[lepton]]s, [[quark]]s, and the fundamental [[boson]]s. [[Subatomic particle]]s such as [[proton]]s or [[neutron]]s, which [[Quark|contain]] two or more elementary particles, are known as [[composite particle]]s.

Ordinary matter is composed of [[atom]]s, themselves once thought to be indivisible elementary particles. The name ''atom'' comes from the Ancient Greek word ''ἄτομος'' ([[wiktionary:átomo#:~:text=Learned borrowing from Latin atomus,, “to cut”).|atomos]]) which means ''indivisible'' or ''uncuttable''. Despite the [[Democritus|theories about atoms]] that had existed for [[De rerum natura|thousands of years]], the factual existence of atoms remained controversial until 1905. In that year, [[Albert Einstein]] published [[Über die von der molekularkinetischen Theorie der Wärme geforderte Bewegung von in ruhenden Flüssigkeiten suspendierten Teilchen|his paper]] on [[Brownian motion]], putting to rest theories that had regarded [[molecule]]s as mathematical illusions. Einstein subsequently identified matter as ultimately composed of various concentrations of [[Mass–energy equivalence|energy]].<ref name=PFI /><ref>
{{cite journal
 |first1=Ronald |last1=Newburgh
 |first2=Joseph |last2=Peidle
 |first3=Wolfgang |last3=Rueckner
 |year=2006
 |title=Einstein, Perrin, and the reality of atoms: 1905 revisited
 |url=http://physlab.lums.edu.pk/images/f/fe/Ref1.pdf
 |journal=[[American Journal of Physics]]
 |volume=74
 |issue=6
 |pages=478–481
 |bibcode=2006AmJPh..74..478N
 |doi=10.1119/1.2188962
 |access-date=2013-08-17
 |archive-url=https://web.archive.org/web/20170803105918/https://physlab.lums.edu.pk/images/f/fe/Ref1.pdf
 |archive-date=2017-08-03 |df=dmy-all
 |url-status=dead
}}</ref>

Subatomic constituents of the atom were first identified toward the end of the [[19th century in science|19th century]], beginning with the [[J. J. Thomson#Discovery of the electron|electron]], followed by the [[Ernest Rutherford#Discovery of the proton|proton]] in 1919, the [[photon]] in the 1920s, and the [[Discovery of the neutron|neutron]] in 1932.<ref name="PFI" /> By that time, the advent of [[quantum mechanics]] had [[History of quantum mechanics|radically altered]] the definition of a "particle" by putting forward an understanding in which they carried out a simultaneous existence as [[matter wave]]s.<ref>
{{cite book
 |first=Friedel |last=Weinert
 |year=2004
 |title=The Scientist as Philosopher: Philosophical consequences of great scientific discoveries
 |publisher=[[Springer (publisher)|Springer]]
 |pages=43, 57–59
 |url=https://books.google.com/books?id=E0NRcFEjvU4C&pg=PA43
 |isbn=978-3-540-20580-7
 |bibcode=2004sapp.book.....W
}}</ref><ref name="Kuhlmann">
{{cite magazine
 |first=Meinard |last=Kuhlmann
 |date=24 July 2013
 |url=http://www.scientificamerican.com/article.cfm?id=physicists-debate-whether-world-made-of-particles-fields-or-something-else
 |title=Physicists debate whether the world is made of particles or fields – or something else entirely
 |magazine=[[Scientific American]]
}}</ref>

Many theoretical elaborations upon, and [[Physics beyond the Standard Model|beyond]], the Standard Model have been made since its [[Standard Model#Historical background|codification]] in the 1970s. These include notions of [[supersymmetry]], which double the number of elementary particles by hypothesizing that each known particle associates with a "shadow" partner far more massive.<ref>
{{cite web
 |collaboration=Particle Data Group
 |publisher=[[Berkeley Lab]]
 |url=http://www.particleadventure.org/supersymmetry.html
 |title=Unsolved mysteries: Supersymmetry
 |work=The Particle Adventure
 |access-date=2013-08-28 |df=dmy-all
}}</ref><ref>
{{cite book
 |collaboration=National Research Council
 |year=2006
 |title=Revealing the Hidden Nature of Space and Time: Charting the Course for Elementary Particle Physics
 |page=68
 |publisher=[[National Academies Press]]
 |url=https://books.google.com/books?id=zXoZjZFZF-kC&pg=PA68
 |isbn=978-0-309-66039-6
 |bibcode=2006rhns.book......
}}</ref> However, like an [[Graviton|additional elementary boson]] mediating gravitation, such [[superpartner]]s remain undiscovered as of 2025.<ref name="ONeill">{{cite news |last=O'Neill |first=Ian |date=24 Jul 2013 |title=LHC discovery maims supersymmetry, again |website=[[Discovery News]] |url=http://news.discovery.com/space/lhc-discovery-maims-supersymmetry-again-130724.htm |url-status=dead |access-date=2013-08-28 |archive-url=https://web.archive.org/web/20160313000505/http://news.discovery.com/space/lhc-discovery-maims-supersymmetry-again-130724.htm |archive-date=2016-03-13 |df=dmy-all}}</ref><ref>
{{cite web
 |url=http://phys.org/news/2013-07-cern-latest-supersymmetry.html
 |title=CERN latest data shows no sign of supersymmetry – yet
 |work=[[Phys.Org]]
 |date=25 Jul 2013
 |access-date=2013-08-28 |df=dmy-all
}}</ref><ref name=PFI />{{update inline|date=January 2025}}