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Fix Matter see-also invoke

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imported>WikiHarold: Fix Matter see-also invoke

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Fix Matter see-also invoke

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{{Short description|Subatomic particle having no known substructure}}

{{Quantum matter backlink|Particles}}

An '''elementary particle''' or '''fundamental particle''' is a [[Physics:Quantum particle|subatomic particle]] that is not known to be composed of smaller particles.<ref name=PFI /> In the [[Physics:Quantum Standard Model|Standard Model]], elementary particles include [[Physics:Quantum fermion|fermions]], [[Physics:Quantum boson|bosons]], [[Physics:Quantum quark|quarks]], [[Physics:Quantum lepton|leptons]], gauge bosons, and the Higgs boson.

<div style="float:right; border:1px solid #e0d890; background:#fff8cc; padding:6px; margin:0 0 1em 1em; width:460px;">
[[File:Elementary Particles.png|440px]]
<div style="font-size:90%;">Sketch overview of elementary particles, interactions, antimatter, and composite particle structure within the Standard Model.</div>
</div>

== Description ==
The Standard Model recognizes seventeen distinct elementary particles: twelve fermions and five bosons. Because of flavour, color charge, and antimatter combinations, these particles appear in a larger number of physical variations.<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>

Elementary particles are distinguished from composite particles. For example, [[Physics:Quantum proton|protons]] and [[Physics:Quantum neutron|neutrons]] are not elementary, because they are made of quarks. By contrast, electrons, quarks, photons, gluons, and neutrinos are treated as elementary in the Standard Model.

The concept of an elementary particle depends on the theoretical framework used.<ref>{{Cite magazine |last=Weinberg |first=Steven |author-link=Steven Weinberg |year=1997 |url=https://purl.stanford.edu/pp223jq9682 |title=What is an elementary particle? |journal=Beam Line. |publisher=Stanford Linear Accelerator |language=en |volume=27 |issue=1}}</ref>

== History ==
Atoms were once regarded as indivisible elementary particles. The word ''atom'' comes from the Greek ''atomos'', meaning indivisible or uncuttable. The physical reality of atoms remained debated until the early twentieth century, when Einstein’s analysis of Brownian motion supported the atomic interpretation of matter.<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
}}</ref>

Subatomic constituents were identified beginning with the [[Physics:Quantum atoms/electron|electron]] near the end of the nineteenth century, followed by the proton, photon, and neutron.<ref name="PFI" /> Quantum mechanics then changed the meaning of the word particle by showing that particles also behave as matter waves.<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>

Since the Standard Model was developed in the 1970s, many extensions have been proposed. Supersymmetry, for example, predicts heavier partner particles for known elementary particles, but such superpartners have not been discovered.<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
}}</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><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 |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}}</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
}}</ref><ref name=PFI />

== Standard Model overview ==
All elementary particles are either fermions or bosons. Fermions obey Fermi–Dirac statistics and have half-integer spin. Bosons obey Bose–Einstein statistics and have integer spin.<ref name=PFI>{{cite book
|first1=Sylvie |last1=Braibant
|first2=Giorgio |last2=Giacomelli
|first3=Maurizio |last3=Spurio
|year=2012
|title=Particles and Fundamental Interactions: An introduction to particle physics
|url=https://books.google.com/books?id=e8YUUG2pGeIC&pg=PA384
|edition=2nd
|publisher=[[Springer (publisher)|Springer]]
|isbn=978-94-007-2463-1
|pages=1–3
}}</ref>

In the Standard Model, elementary particles are represented as point particles for predictive calculations. The model is highly successful but incomplete, because it does not include gravity and contains parameters that are measured rather than explained from deeper principles.<ref>{{harvnb|Braibant|Giacomelli|Spurio|2012|p=384}}</ref>

== Fundamental fermions ==
The twelve fundamental fermions are divided into three generations. Each generation contains two quarks and two leptons.

{| class="wikitable" style="text-align:center;"
|+ Particle generations
|-
! colspan="6" | Leptons
|-
| colspan="2" | First generation
| colspan="2" | Second generation
| colspan="2" | Third generation
|-
| Electron || Electron neutrino
| Muon || Muon neutrino
| Tau || Tau neutrino
|-
! colspan="6" | Quarks
|-
| colspan="2" | First generation
| colspan="2" | Second generation
| colspan="2" | Third generation
|-
| Up quark || Down quark
| Charm quark || Strange quark
| Top quark || Bottom quark
|}

Half of the fundamental fermions are leptons. The charged leptons are the electron, muon, and tau. The neutral leptons are the electron neutrino, muon neutrino, and tau neutrino.

The remaining six fermions are quarks. Quarks carry color charge and fractional electric charge.

== Fermion masses ==
The measured masses of elementary fermions vary greatly. Neutrino masses are extremely small, while the top quark is the most massive known elementary fermion.<ref>{{cite journal |last1=Navas |first1=S. |collaboration=Particle Data Group |title=Review of Particle Physics |journal=[[Physical Review D]] |volume=110 |issue=3 |date=2024-08-01 |article-number=030001 |doi=10.1103/PhysRevD.110.030001 |bibcode=2024PhRvD.110c0001N |hdl=11384/149923 |hdl-access=free }}</ref>

Quark masses cannot be measured in isolation because quarks are confined inside hadrons. Their quoted masses therefore depend on the quantum chromodynamics scheme used.

== Antiparticles ==
Each fundamental fermion has a corresponding antiparticle. The electron’s antiparticle is the positron, which has the same mass as the electron but opposite electric charge.

Antimatter particles have opposite quantum numbers from their corresponding matter particles. When a particle and its antiparticle meet, they may annihilate into other particles or photons.

== Quarks ==
Quarks and antiquarks have never been observed as isolated particles, a fact explained by color confinement. Quarks carry one of three color charges, while antiquarks carry corresponding anticolors.

Color-charged particles interact through gluon exchange. Unlike electromagnetism, the strong force does not weaken in a simple way as quarks separate; instead, increasing separation produces stronger confinement effects.<ref>{{cite web|url=https://www.britannica.com/science/strong-force|title=Strong force|author=Christine Sutton|publisher=Britannica}}</ref>

Quarks combine into color-neutral composite particles called hadrons. A quark and antiquark form a meson. Three quarks form a baryon, such as a proton or neutron.

== Fundamental bosons ==
Fundamental bosons include gauge bosons and the Higgs boson. Gauge bosons mediate interactions, while the Higgs boson is associated with the origin of mass through the Higgs mechanism.

=== Gluons ===
Gluons mediate the strong interaction. They bind quarks into hadrons, including baryons and mesons. Gluons themselves carry color and anticolor charge, producing eight gluon variations in the Standard Model.

=== Electroweak bosons ===
The electroweak bosons are the photon, W<sup>+</sup>, W<sup>−</sup>, and Z<sup>0</sup>. The photon mediates electromagnetism. The W and Z bosons mediate the weak interaction.

The weak interaction is responsible for processes such as beta decay. The Z boson can mediate neutral-current interactions, including elastic scattering of neutrinos.

=== Higgs boson ===
The Higgs boson is a spin-0 boson associated with the Higgs field. The Higgs mechanism explains why the W and Z bosons are massive while the photon remains massless.

On 4 July 2012, CERN announced observation of a new particle consistent with the Higgs boson.<ref>{{cite news
|first=Lizzy |last=Davies
|date=4 July 2014
|title=Higgs boson announcement live: CERN scientists discover subatomic particle
|url=https://www.theguardian.com/science/blog/2012/jul/04/higgs-boson-discovered-live-coverage-cern
|newspaper=[[The Guardian]]
|access-date=2012-07-06
}}</ref> It has a mass of about 125 GeV/c<sup>2</sup>.<ref>{{cite web
|first=Lucas |last=Taylor
|date=4 Jul 2014
|title=Observation of a new particle with a mass of 125 GeV
|url=http://cms.web.cern.ch/news/observation-new-particle-mass-125-gev
|publisher=[[Compact Muon Solenoid|CMS]]
|access-date=2012-07-06
}}</ref>

== Cosmic abundance ==
Most visible mass in the universe is contained in protons and neutrons. These are baryons made mainly of up and down quarks. Some estimates suggest that the observable universe contains roughly 10<sup>80</sup> baryons.<ref>{{Cite journal |last=Padilla |first=Antonio |date=2022-08-13 |title=The universe by numbers |url=https://linkinghub.elsevier.com/retrieve/pii/S0262407922014476 |journal=New Scientist |volume=255 |issue=3399 |pages=42–45 |doi=10.1016/S0262-4079(22)01447-6 |bibcode=2022NewSc.255...42P |issn=0262-4079|url-access=subscription }}</ref>

In terms of particle number, neutrinos and photons are extremely abundant in the visible universe.<ref name=mrob>{{cite web
|first=Robert |last=Munafo
|date=24 Jul 2013
|title=Notable Properties of Specific Numbers
|url=http://mrob.com/pub/math/numbers-19.html
|access-date=2013-08-28
}}</ref>

== Beyond the Standard Model ==
The Standard Model does not explain every feature of nature. It does not include gravity, does not explain the hierarchy between weak and gravitational forces, and leaves some parameters unexplained.

=== Graviton ===
The graviton is a hypothetical spin-2 boson proposed to mediate gravity. It has not been detected.<ref name="PFI" /> Some models include massive Kaluza–Klein gravitons.<ref>{{cite journal |last1=Calmet |first1=Xavier |last2=de Aquino |first2=Priscila |last3=Rizzo |first3=Thomas G. |year=2010 |title=Massless versus Kaluza-Klein gravitons at the LHC |journal=Physics Letters B |volume=682 |issue=4–5 |pages=446–449 |arxiv=0910.1535 |bibcode=2010PhLB..682..446C |doi=10.1016/j.physletb.2009.11.045 |hdl=2078/31706 |s2cid=16310404}}</ref>

=== Grand unification ===
Grand unified theories attempt to combine the strong, weak, and electromagnetic interactions into a single interaction at very high energy. Some simple grand unified models predict proton decay, which has not been observed.

=== Supersymmetry ===
Supersymmetry proposes a symmetry between fermions and bosons. It predicts supersymmetric partner particles such as sleptons, squarks, neutralinos, and charginos. These particles have not been experimentally confirmed.

=== String theory ===
String theory proposes that particles are excitations of tiny one-dimensional strings. Different vibrational modes correspond to different particle properties such as mass, charge, and spin. Some versions of string theory require extra dimensions and predict a massless spin-2 particle resembling the graviton.<ref>{{cite journal |doi=10.1016/0550-3213(96)00172-1 |arxiv=hep-th/9602022 |bibcode=1996NuPhB.469..403V |title=Evidence for F-theory |year=1996 |last1=Vafa |first1=Cumrun |author-link1=Cumrun Vafa |journal=Nuclear Physics B |volume=469 |issue=3 |pages=403–415|s2cid=6511691 }}</ref>

=== Technicolor and preons ===
Technicolor theories propose new strong interactions in which the Higgs boson may be composite rather than elementary. Preon theories suggest that some particles currently considered elementary may themselves be made of more fundamental constituents.

=== Accelerons ===
Accelerons are hypothetical particles proposed in models linking neutrino mass to dark energy and the accelerating expansion of the universe.<ref name=acceleron>{{cite web
|date=28 Jul 2004
|url=https://www.sciencedaily.com/releases/2004/07/040728090338.htm
|title=New theory links neutrino's slight mass to accelerating Universe expansion
|website=[[ScienceDaily]]
|access-date=2008-06-05
}}</ref><ref>{{cite news
|url=https://astronomy.com/news/2004/07/acceleron-anyone
|title=Acceleron, anyone?
|first=Francis |last=Reddy
|date=2004-07-27
|magazine=Astronomy
|access-date=2020-04-20
}}</ref>

== Physical interpretation ==
Elementary particles are the smallest known excitations of quantum fields in the Standard Model. Their interactions, masses, charges, and quantum numbers determine the structure of atoms, nuclei, radiation, and ordinary matter.

== Properties ==

* no known internal substructure
* classified as fermions or bosons
* described by quantum field theory
* includes quarks, leptons, gauge bosons, and the Higgs boson
* forms composite particles such as protons, neutrons, mesons, and atoms
* central to the Standard Model and searches for physics beyond it

=See also=
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}}

=References=
{{reflist|3}}

{{Author|Harold Foppele}}

{{Sourceattribution|Elementary particle|1}}

Physics:Quantum elementary particle - Revision history

imported>WikiHarold: Fix Matter see-also invoke

imported>WikiHarold: Fix Matter see-also invoke