Editing Antiparticle

{{short description|Particle with opposite charges}}
[[Image:Particles and antiparticles.svg|thumb|alt=Diagram illustrating the particles and antiparticles of electron, neutron and proton, as well as their "size" (not to scale). It is easier to identify them by looking at the total mass of both the antiparticle and particle. On the left, from top to bottom, is shown an electron (small red dot), a proton (big blue dot), and a neutron (big dot, black in the middle, gradually fading to white near the edges). On the right, from top to bottom, are shown the anti electron (small blue dot), anti proton (big red dot) and anti neutron (big dot, white in the middle, fading to black near the edges).|Illustration of electric charge of [[particle]]s (left) and antiparticles (right). From top to bottom; [[electron]]/[[positron]], [[proton]]/[[antiproton]], [[neutron]]/[[antineutron]].]]
{{antimatter}}
In [[particle physics]], every type of [[particle]] of "ordinary" matter (as opposed to [[antimatter]]) is associated with an '''antiparticle''' with the same [[mass]] but with opposite [[charge (physics)|physical charges]] (such as [[electric charge]]). For example, the antiparticle of the [[electron]] is the [[positron]] (also known as an antielectron). While the electron has a negative electric charge, the positron has a positive electric charge, and is produced naturally in certain types of [[radioactive decay]].  The opposite is also true: the antiparticle of the positron is the electron.

Some particles, such as the [[photon]], are their own antiparticle. Otherwise, for each pair of antiparticle partners, one is designated as the normal particle (the one that occurs in matter usually interacted with in daily life). The other (usually given the prefix "anti-") is designated the ''antiparticle''.

Particle–antiparticle pairs can [[particle annihilation|annihilate]] each other, producing photons; since the charges of the particle and antiparticle are opposite, total charge is conserved. For example, the positrons produced in natural radioactive decay quickly annihilate themselves with electrons, producing pairs of [[gamma ray]]s, a process exploited in [[positron emission tomography]].

The laws of nature are very nearly symmetrical with respect to particles and antiparticles. For example, an [[antiproton]] and a [[positron]] can form an [[antihydrogen]] [[atom]], which is believed to have the same properties as a [[hydrogen]] atom. This leads to the question of why the [[baryogenesis|formation of matter after the Big Bang]] resulted in a universe consisting almost entirely of matter, rather than being a half-and-half mixture of matter and [[antimatter]]. The discovery of [[CP violation|charge parity violation]] helped to shed light on this problem by showing that this symmetry, originally thought to be perfect, was only approximate. The question about how the [[baryogenesis|formation of matter after the Big Bang]] resulted in a universe consisting almost entirely of matter remains an unanswered one, and explanations so far are not truly satisfactory, overall. 

Because [[Charge (physics)|charge]] is [[Charge conservation|conserved]], it is not possible to create an antiparticle without either destroying another particle of the same charge (as is for instance the case when antiparticles are produced naturally via [[beta decay]] or the collision of [[cosmic ray]]s with Earth's atmosphere), or by the simultaneous creation of both a particle ''and'' its antiparticle (pair production), which can occur in [[particle accelerator]]s such as the [[Large Hadron Collider]] at [[CERN]].

Particles and their antiparticles have equal and opposite charges, so that an uncharged particle also gives rise to an uncharged antiparticle.  In many cases, the antiparticle and the particle coincide: pairs of [[photon]]s, [[W and Z bosons#Z boson|Z<sup>0</sup>&nbsp;bosons]], [[Pi meson|{{SubatomicParticle|Pion0}}]]&nbsp;[[meson]]s, and hypothetical [[graviton]]s and some hypothetical [[Weakly interacting massive particle|WIMP]]s all self-annihilate.  However, electrically neutral particles need not be identical to their antiparticles:  for example, the neutron and antineutron are distinct.

== History ==

=== Experiment ===

In 1932, soon after the prediction of [[positron]]s by [[Paul Dirac]], [[Carl D. Anderson]] found that cosmic-ray collisions produced these particles in a [[cloud chamber]] – a [[particle detector]] in which moving [[electron]]s (or positrons) leave behind trails as they move through the gas. The electric charge-to-mass ratio of a particle can be measured by observing the radius of curling of its cloud-chamber track in a [[magnetic field]]. Positrons, because of the direction that their paths curled, were at first mistaken for electrons travelling in the opposite direction.  Positron paths in a cloud-chamber trace the same helical path as an electron but rotate in the opposite direction with respect to the magnetic field direction due to their having the same magnitude of charge-to-mass ratio but with opposite charge and, therefore, opposite signed charge-to-mass ratios.

The [[antiproton]] and [[antineutron]] were found by [[Emilio Segrè]] and [[Owen Chamberlain]] in 1955 at the [[University of California, Berkeley]].<ref>{{cite web|url=https://www.nobelprize.org/prizes/physics/1959/summary/|title=The Nobel Prize in Physics 1959}}</ref> Since then, the antiparticles of many other subatomic particles have been created in particle accelerator experiments. In recent years, complete atoms of [[antimatter]] have been assembled out of antiprotons and positrons, collected in electromagnetic traps.<ref>{{cite web|url=http://news.nationalgeographic.com/news/2010/11/101118-antimatter-trapped-engines-bombs-nature-science-cern/|archive-url=https://web.archive.org/web/20101120181454/http://news.nationalgeographic.com/news/2010/11/101118-antimatter-trapped-engines-bombs-nature-science-cern/|url-status=dead|archive-date=November 20, 2010|title=Antimatter Atoms Trapped for First Time – 'A Big Deal'|date=19 November 2010}}</ref>

=== Dirac hole theory ===
{{quote box|quote=... the development of [[quantum field theory]] made the interpretation of antiparticles as holes unnecessary, even though it lingers on in many textbooks.|source=[[Steven Weinberg]]<ref>{{cite book|last=Weinberg|first=Steve|title=The quantum theory of fields, Volume 1 : Foundations|isbn=0-521-55001-7|page=[https://archive.org/details/quantumtheoryoff00stev/page/14 14]|year=1995|publisher=Cambridge University Press |url-access=registration|url=https://archive.org/details/quantumtheoryoff00stev/page/14}}</ref>|width=300px}}
Solutions of the [[Dirac equation]] contain negative energy quantum states. As a result, an electron could always radiate energy and fall into a negative energy state. Even worse, it could keep radiating infinite amounts of energy because there were infinitely many negative energy states available. To prevent this unphysical situation from happening, Dirac proposed that a "sea" of negative-energy electrons fills the universe, already occupying all of the lower-energy states so that, due to the [[Pauli exclusion principle]], no other electron could fall into them. Sometimes, however, one of these negative-energy particles could be lifted out of this [[Dirac sea]] to become a positive-energy particle. But, when lifted out, it would leave behind a ''[[electron hole|hole]]'' in the sea that would act exactly like a positive-energy electron with a reversed charge. These holes were interpreted as "negative-energy electrons" by Paul Dirac and mistakenly  identified  with [[proton]]s in his 1930 paper ''A Theory of Electrons and Protons''<ref>
{{cite journal
 |last1=Dirac |first1=Paul
 |date=1930
 |title=A Theory of Electrons and Protons
 |journal=[[Proceedings of the Royal Society A]]
 |volume=126 |issue= 801|pages=360–365
 |doi=10.1098/rspa.1930.0013
|bibcode = 1930RSPSA.126..360D |doi-access=free}}</ref> However, these "negative-energy electrons" turned out to be [[positron]]s, and not [[proton]]s.

This picture implied an infinite negative charge for the universe{{snd}}a problem of which Dirac was aware. Dirac tried to argue that we would perceive this as the normal state of zero charge. Another difficulty was the difference in masses of the electron and the proton. Dirac tried  to argue that this was due to the electromagnetic interactions with the sea, until [[Hermann Weyl]] proved that hole theory was completely symmetric between negative and positive charges. Dirac also predicted a reaction {{Subatomic particle|Electron}}&nbsp;+&nbsp;{{Subatomic particle|Proton+}}&nbsp;→&nbsp;{{Subatomic particle|Photon}}&nbsp;+&nbsp;{{Subatomic particle|Photon}}, where an electron and a proton annihilate to give two photons. [[Robert Oppenheimer]] and [[Igor Tamm]], however,  proved that this would cause ordinary matter to disappear too fast. A year later, in 1931, Dirac modified his theory and postulated the [[positron]], a new particle of the same mass as the electron. The discovery of this particle the next year removed the last two objections to his theory.

Within Dirac's theory, the problem of infinite charge of the universe remains. Some [[boson]]s also have antiparticles, but since bosons do not obey the [[Pauli exclusion principle]] (only [[fermion]]s do), hole theory does not work for them. A unified interpretation of antiparticles is now available in [[quantum field theory]], which solves both these problems by describing antimatter as negative energy states of the same underlying matter field, i.e. particles moving backwards in time.<ref>{{Cite book|url=https://books.google.com/books?id=Y-0kAwAAQBAJ&pg=PA61|title=Quantum Field Theory for the Gifted Amateur|last1=Lancaster|first1=Tom|last2=Blundell|first2=Stephen J.|last3=Blundell|first3=Stephen|date= 2014|publisher=OUP Oxford|isbn=978-0199699339|page=61|language=en}}</ref>

== Elementary antiparticles ==
{| class="wikitable"
|+Antiquarks
!Generation
!Name
!Symbol
!Spin
!Charge ([[Elementary charge|e]])
!Mass ([[Electronvolt|MeV]]/[[Speed of light|''c'']]<sup>2</sup>) <ref name="PDG2016">{{cite journal |author=Particle Data Group |year=2016 |title=Review of Particle Physics |url=https://cds.cern.ch/record/2241948 |journal=Chinese Physics C |volume=40 |issue=10 |pages=100001 |bibcode=2016ChPhC..40j0001P |doi=10.1088/1674-1137/40/10/100001 |s2cid=125766528 |hdl-access=free |hdl=1983/c6dc3926-daee-4d0e-9149-5ff3a8120574}}</ref>
!Observed
|-
| rowspan="2" |1
|[[Up quark|up antiquark]]
|{{Subatomic particle|up antiquark}}
|{{frac|1|2}}
|−{{frac|2|3}}
|{{val|2.2|0.6|0.4}}
|Yes
|-
|[[Down quark|down antiquark]]
|{{Subatomic particle|down antiquark}}
|{{frac|1|2}}
| +{{frac|1|3}}
|{{val|4.6|0.5|0.4}}
|Yes
|-
| rowspan="2" |2
|[[Charm quark|charm antiquark]]
|{{Subatomic particle|charm antiquark}}
|{{frac|1|2}}
|−{{frac|2|3}}
|{{val|1,280|30}}
|Yes
|-
|[[Strange quark|strange antiquark]]
|{{Subatomic particle|strange antiquark}}
|{{frac|1|2}}
| +{{frac|1|3}}
|{{val|96|8|4}}
|Yes
|-
| rowspan="2" |3
|[[Top quark|top antiquark]]
|{{Subatomic particle|top antiquark}}
|{{frac|1|2}}
|−{{frac|2|3}}
|{{val|173100|600}}
|Yes
|-
|[[Bottom quark|bottom antiquark]]
|{{Subatomic particle|bottom antiquark}}
|{{frac|1|2}}
| +{{frac|1|3}}
|{{val|4,180|40|30}}
|Yes
|}
{| class="wikitable"
|+Antileptons
!Generation
!Name
!Symbol
!Spin
!Charge ([[Elementary charge|e]])
!Mass ([[Electronvolt|MeV]]/[[Speed of light|''c'']]<sup>2</sup>) <ref name="PDG2016" />
!Observed
|-
| rowspan="2" |1
|[[positron]]
|{{Subatomic particle|positron}}
|{{sfrac| 1 |2}}
| +1
|0.511
|Yes
|-
|[[electron antineutrino]]
|{{math|{{Subatomic particle|electron antineutrino}}}}
|{{sfrac| 1 |2}}
|{{figure space}}0
|{{nobr|< 0.0000022}}
|Yes
|-
| rowspan="2" |2
|[[Muon|antimuon]]
|{{math|{{Subatomic particle|antimuon}}}}
|{{sfrac| 1 |2}}
| +1
|105.7
|Yes
|-
|[[Muon neutrino|muon antineutrino]]
|{{math|{{Subatomic particle|muon antineutrino}}}}
|{{sfrac| 1 |2}}
|{{figure space}}0
|{{nobr|< 0.170}}
|Yes
|-
| rowspan="2" |3
|[[Tau (particle)|antitau]]
|{{math|{{Subatomic particle|antitau}}}}
|{{sfrac| 1 |2}}
| +1
|{{val|1,776.86|0.12}}
|Yes
|-
|[[Tau neutrino|tau antineutrino]]
|{{math|{{Subatomic particle|tau antineutrino}}}}
|{{sfrac| 1 |2}}
|{{figure space}}0
|{{nobr|< 15.5}}
|Yes
|}
{| class="wikitable"
|+Antibosons
!Name
!Symbol
!Spin
!Charge ([[Elementary charge|''e'']])
!Mass (GeV/''c''<sup>2</sup>) <ref name="PDG20162">{{cite journal |author=Particle Data Group |year=2016 |title=Review of Particle Physics |url=https://cds.cern.ch/record/2241948 |journal=Chinese Physics C |volume=40 |issue=10 |pages=100001 |bibcode=2016ChPhC..40j0001P |doi=10.1088/1674-1137/40/10/100001 |s2cid=125766528 |hdl-access=free |hdl=1983/c6dc3926-daee-4d0e-9149-5ff3a8120574}}</ref>
!Interaction mediated
!Observed
|-
|[[W and Z bosons|anti W boson]]
|{{Subatomic particle|W Boson+}}
|1
| +1
|{{val|80.385|0.015}}
|[[weak interaction]]
|Yes
|}

== Composite antiparticles ==
{| class="wikitable"
|+
!Class
!Subclass
!Name
!Symbol
!Spin
!Charge 
([[Elementary charge|''e'']])
!Mass ([[Electronvolt#Mass|MeV/''c''<sup>2</sup>]]) 
!Mass (kg)
!Observed
|-
| rowspan="2" |[[Hadron|Antihadron]]
| rowspan="2" |[[Antibaryon]]
|[[Antiproton]]
|{{SubatomicParticle|Antiproton}}
|{{sfrac| 1 |2}}
|−1
|938.27208943(29)<ref>{{Cite web |title=CODATA Value: proton mass energy equivalent in MeV |url=https://physics.nist.gov/cgi-bin/cuu/Value?mpc2mev |access-date=2024-09-08 |website=physics.nist.gov}}</ref>
|1.67262192595(52)×10<sup>−27</sup><ref>{{Cite web |title=CODATA Value: proton mass |url=https://physics.nist.gov/cgi-bin/cuu/Value?mp |access-date=2024-09-08 |website=physics.nist.gov}}</ref>
|Yes
|-
|[[Antineutron]]
|{{SubatomicParticle|Antineutron}}
|{{sfrac| 1 |2}}
|0
|939.56542194(48)<ref>{{Cite web |title=CODATA Value: neutron mass energy equivalent in MeV |url=https://physics.nist.gov/cgi-bin/cuu/Value?mnc2mev |access-date=2024-09-08 |website=physics.nist.gov}}</ref>
|?
|Yes
|}

== Particle–antiparticle annihilation ==
{{main|Annihilation}}
[[Image:kkbar had.svg|frame|alt=Feynman diagram of a kaon oscillation. A straight red line suddenly turns purple, showing a kaon changing into an antikaon. A medallion is show zooming in on the region where the line changes color. The medallion shows that the line is not straight, but rather that at the place the kaon changes into an antikaon, the red line breaks into two curved lines, corresponding the production of virtual pions, which rejoin into the violet line, corresponding to the annihilation of the virtual pions. |An example of a virtual [[pion]] pair that influences the propagation of a [[kaon]], causing a neutral kaon to ''mix'' with the antikaon. This is an example of [[renormalization]] in [[quantum field theory]] – the field theory being necessary because of the change in particle number.]]

If a particle and antiparticle are in the appropriate quantum states, then they can annihilate each other and produce other particles. Reactions such as {{Subatomic particle|Electron}}&nbsp;+&nbsp;{{Subatomic particle|Positron}}&nbsp;→&nbsp;{{Subatomic particle|Photon}}{{Subatomic particle|Photon}} (the two-photon annihilation of an electron-positron pair) are an example. The single-photon annihilation of an electron-positron pair, {{Subatomic particle|Electron}}&nbsp;+&nbsp;{{Subatomic particle|Positron}}&nbsp;→&nbsp;{{Subatomic particle|Photon}}, cannot occur in free space because it is impossible to conserve energy and [[momentum]] together in this process. However, in the Coulomb field of a nucleus the [[translational invariance]] is broken and single-photon annihilation may occur.<ref>
{{cite journal
 | last=Sodickson | first=L.
 |author2=W. Bowman |author3=J. Stephenson
  | date = 1961
 | title = Single-Quantum Annihilation of Positrons
 | journal = [[Physical Review]]
 | volume = 124  | issue = 6 | pages = 1851–1861
 | bibcode = 1961PhRv..124.1851S
 | doi = 10.1103/PhysRev.124.1851
}}</ref> The reverse reaction (in free space, without an atomic nucleus) is also impossible for this reason. In quantum field theory, this process is allowed only as an intermediate quantum state for times short enough that the violation of energy conservation can be accommodated by the [[uncertainty principle]]. This opens the way for virtual pair production or annihilation in which a one particle quantum state may ''fluctuate'' into a two particle state and back. These processes are important in the [[vacuum state]] and [[renormalization]] of a quantum field theory. It also opens the way for neutral particle mixing through processes such as the one pictured here, which is a complicated example of [[mass renormalization]].

== Properties ==

[[Quantum state]]s of a particle and an antiparticle are interchanged by the combined application of [[C-symmetry|charge conjugation]] <math> C </math>, [[P-symmetry|parity]] <math> P </math> and [[T-symmetry|time reversal]] <math> T </math>.
<math> C </math> and <math> P </math> are linear, unitary operators, <math> T </math> is antilinear and antiunitary, 
<math> \langle \Psi | T\,\Phi\rangle = \langle \Phi | T^{-1}\,\Psi\rangle </math>. 
If <math>|p,\sigma ,n \rangle </math> denotes the quantum state of a particle <math> n </math>  with momentum <math> p </math> and spin <math> J </math> whose component in the z-direction is <math> \sigma </math>, then one has
::<math>CPT \ |p,\sigma,n \rangle\ =\ (-1)^{J-\sigma}\ |p,-\sigma,n^c \rangle ,</math>
where <math> n^c </math> denotes the charge conjugate state, that is, the antiparticle. In particular a massive particle and its antiparticle transform under the same [[irreducible representation]] of the [[Poincaré group]] which means the antiparticle has the same mass and the same spin.

If <math>C</math>, <math>P</math> and <math>T</math> 
can be defined separately on the particles and antiparticles, then
::<math>T\ |p,\sigma,n\rangle \ \propto \ |-p,-\sigma,n\rangle ,</math>
::<math>CP\ |p,\sigma,n\rangle \ \propto \ |-p,\sigma,n^c\rangle ,</math>
::<math>C\ |p,\sigma,n\rangle \ \propto \ |p,\sigma,n^c\rangle ,</math>
where the proportionality sign indicates that there might be a phase on the right hand side.

As <math> CPT </math> anticommutes with the charges, <math> CPT\,Q = - Q\, CPT </math>, particle and antiparticle have opposite [[electric charge]]s q and -q.

== Quantum field theory ==
:''This section draws upon the ideas, language and notation of [[canonical quantization]] of a [[quantum field theory]].''

One may try to quantize an electron [[field (physics)|field]] without mixing the annihilation and creation operators by writing

::<math>\psi (x)=\sum_{k}u_k (x)a_k e^{-iE(k)t},\,</math>

where we use the symbol ''k'' to denote the quantum numbers ''p'' and σ of the previous section and the sign of the energy, ''E(k)'', and ''a<sub>k</sub>'' denotes the corresponding annihilation operators. Of course, since we are dealing with [[fermion]]s, we have to have the operators satisfy canonical anti-commutation relations. However, if one now writes down the [[Hamiltonian (quantum mechanics)|Hamiltonian]]

::<math>H=\sum_{k} E(k) a^\dagger_k a_k,\,</math>

then one sees immediately that the expectation value of ''H'' need not be positive. This is because ''E(k)'' can have any sign whatsoever, and the combination of creation and annihilation operators has expectation value 1 or 0.

So one has to introduce the charge conjugate ''antiparticle'' field, with its own creation and annihilation operators satisfying the relations

::<math>b_{k\prime} = a^\dagger_k\ \mathrm{and}\ b^\dagger_{k\prime}=a_k,\,</math>

where ''k'' has the same ''p'', and opposite σ and sign of the energy. Then one can rewrite the field in the form

::<math>\psi(x)=\sum_{k_+} u_k (x)a_k e^{-iE(k)t}+\sum_{k_-} u_k (x)b^\dagger _k e^{-iE(k)t},\,</math>

where the first sum is over positive energy states and the second over those of negative energy. The energy becomes

::<math>H=\sum_{k_+} E_k a^\dagger _k a_k + \sum_{k_-} |E(k)|b^\dagger_k b_k + E_0,\,</math>

where ''E<sub>0</sub>'' is an infinite negative constant. The [[vacuum state]] is defined as the state with no particle or antiparticle, ''i.e.'', <math>a_k |0\rangle=0</math> and <math>b_k |0\rangle=0</math>. Then the energy of the vacuum is exactly ''E<sub>0</sub>''. Since all energies are measured relative to the vacuum, '''H''' is positive definite. Analysis of the properties of ''a<sub>k</sub>'' and ''b<sub>k</sub>'' shows that one is the annihilation operator for particles and the other for antiparticles. This is the case of a [[fermion]].

This approach is due to [[Vladimir Fock]], [[Wendell Furry]] and [[Robert Oppenheimer]]. If one quantizes a real [[Scalar field theory|scalar field]], then one finds that there is only one kind of annihilation operator; therefore, real scalar fields describe neutral bosons. Since complex scalar fields admit two different kinds of annihilation operators, which are related by conjugation, such fields describe charged bosons.

=== Feynman–Stückelberg interpretation <!--'[[Feynman–Stueckelberg interpretation]]', '[[Feynman-Stueckelberg interpretation]]', '[[Stueckelberg–Feynman interpretation]]', '[[Stueckelberg-Feynman interpretation]]', '[[Feynman–Stückelberg interpretation]]', '[[Feynman-Stückelberg interpretation]]', '[[Stückelberg–Feynman interpretation]]', and '[[Stückelberg-Feynman interpretation]]' redirect here-->===

By considering the propagation of the negative energy modes of the electron field backward in time, [[Ernst Stückelberg]] reached a pictorial understanding of the fact that the particle and antiparticle have equal mass '''m''' and spin '''J''' but opposite charges '''q'''. This allowed him to rewrite [[perturbation theory (quantum mechanics)|perturbation theory]] precisely in the form of diagrams. [[Richard Feynman]] later gave an independent systematic derivation of these diagrams from a particle formalism, and they are now called [[Feynman diagram]]s. Each line of a diagram represents a particle propagating either backward or forward in time. In Feynman diagrams, anti-particles are shown traveling backwards in time relative to normal matter, and vice versa.<ref>{{cite book|author=Griffiths, D.J. |author-link=David J. Griffiths |page=61 |year=2008 |title=Introduction to Elementary Particles |edition=2nd |publisher=[[John Wiley & Sons]] |isbn=978-3-527-40601-2|quote=}}</ref> This technique is the most widespread method of computing [[probability amplitude|amplitudes]] in [[quantum field theory]] today.

Since this picture was first developed by Stückelberg,<ref>Stückelberg, Ernst (1941), "La signification du temps propre en mécanique ondulatoire." ''Helv. Phys. Acta'' '''14''', pp. 322–323.</ref> and acquired its modern form in Feynman's work,<ref>{{cite journal|first=Richard P.|last=Feynman|title=Space-time approach to non-relativistic quantum mechanics|journal= [[Reviews of Modern Physics]]|volume= 20|pages= 367–387|year=1948|doi=10.1103/RevModPhys.20.367|bibcode = 1948RvMP...20..367F|issue=2 |url=https://authors.library.caltech.edu/47756/1/FEYrmp48.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://authors.library.caltech.edu/47756/1/FEYrmp48.pdf |archive-date=2022-10-09 |url-status=live}}</ref> it is called the '''Feynman–Stückelberg interpretation'''<!--boldface per WP:R#PLA--> of antiparticles to honor both scientists.

== See also ==
{{Commons category|Antiparticles}}
{{cols}}
* [[List of particles]]
* [[Antimatter]]
* [[Gravitational interaction of antimatter]]
* [[Parity (physics)|Parity]], [[charge conjugation]], and [[time reversal symmetry]]
* [[CP violation]]s
* [[Quantum field theory]]
* [[Baryogenesis]], [[baryon asymmetry]], and [[Leptogenesis (physics)|Leptogenesis]]
* [[One-electron universe]]
* [[Paul Dirac]]
{{colend}}

== Notes ==
{{Reflist}}

== References ==
*{{cite book
 |last=Feynman
 |first=R. P.
 |date=1987
 |chapter=The reason for antiparticles
 |editor=R. P. Feynman
 |editor2=S. Weinberg
 |title=The 1986 Dirac memorial lectures
 |publisher=[[Cambridge University Press]]
 |isbn=0-521-34000-4
 |url-access=registration
 |url=https://archive.org/details/elementarypartic0000feyn
 }}
*{{cite book
 |last=Weinberg
 |first=S.
 |date=1995
 |title=The Quantum Theory of Fields, Volume 1: Foundations
 |publisher=[[Cambridge University Press]]
 |isbn=0-521-55001-7
 |url-access=registration
 |url=https://archive.org/details/quantumtheoryoff00stev
 }}

== External links ==
* {{TĐBKVN|22322|Phản hạt}}
* [https://home.cern/science/physics/antimatter Antimatter] at CERN

{{Particles}}
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[[Category:Quantum field theory]]
[[Category:Antimatter|Antimatter]]
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