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| | Not much to tell about myself really.<br>Feels good to be a member of this site.<br>I really wish I am useful at all<br><br>Also visit my web blog; [http://hemorrhoidtreatmentfix.com/internal-hemorrhoids-treatment how to treat internal hemorrhoids] |
| {{Standard model of particle physics}}
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| In the [[physics|physical sciences]], '''subatomic particles''' are [[particle]]s smaller than [[atom]]s.<ref>{{cite web|title=Subatomic particles|url=http://www.ndt-ed.org/EducationResources/HighSchool/Radiography/subatomicparticles.htm|publisher=NTD|accessdate=5 June 2012}}</ref> (although some subatomic particles have mass greater than some atoms). There are two types of subatomic particles: [[elementary particle]]s, which according to current theories are not made of other particles; and ''composite'' particles.<ref>{{cite book|last=Bolonkin|first=Alexander|title=Universe, Human Immortality and Future Human Evaluation|year=2011|publisher=Elsevier|isbn=9780124158016|pages=25}}</ref> [[Particle physics]] and [[nuclear physics]] study these particles and how they [[interaction|interact]]<!-- please do not change to [[fundamental interaction]]: what nuclear physics studies by no means isn’t FUNDAMENTAL -->.<ref name=IntroQM1>
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| {{Cite book
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| | last = Fritzsch | first = Harald
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| | year = 2005
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| | title = Elementary Particles
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| | url = http://books.google.com/?id=KFodZ8oHz2sC&printsec=frontcover
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| | pages = 11–20
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| | publisher = [[World Scientific]]
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| | isbn = 978-981-256-141-1
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| }}</ref>
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| In particle physics, the concept of a particle is one of several concepts inherited from [[classical physics]]. But is also reflects the modern understanding that at the [[quantum physics|quantum]] scale [[matter]] and [[energy]] behave very differently from what much of everyday experience would lead us to expect.
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| The idea of a particle underwent serious rethinking in light of experiments that showed that light could behave like a stream of particles (called [[photon]]s) as well as exhibit wave-like properties. This led to the new concept of [[wave–particle duality]] to reflect that quantum-scale "particles" behave like both particles and waves. Another new concept, the [[uncertainty principle]], states that such their properties as [[position (vector)|position]] and [[momentum]] cannot be measured exactly. In more recent times, wave–particle duality has been shown to apply not only to photons but to increasingly massive particles.<ref>
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| {{Cite journal
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| | author =
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| | year = 2000
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| | title = Wave-particle duality of C60 molecules
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| | first6 =Anton
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| | last6 =Zeilinger
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| | first5 =Gerbrand
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| | last5 =Van Der Zouw
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| | first4 =Claudia
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| | last4 =Keller
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| | first3 =Julian
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| | journal = [[Nature (journal)|Nature]]
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| | last3 =Vos-Andreae
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| | volume = 401
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| | first2 =Olaf
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| | doi =10.1038/44348
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| | last2 =Nairz
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| | bibcode = 1999Natur.401..680A |issue= 6754 |pages = 680–682
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| | last1 = Arndt
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| | first1 = Markus
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| | pmid=18494170
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| }}</ref>
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| Interactions of particles in the framework of [[quantum field theory]] are understood as creation and annihilation of ''[[quantum|quanta]]'' of corresponding [[fundamental interaction]]s. This blends particle physics with [[Quantum field theory|field theory]].
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| ==Classification==
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| === By statistics===
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| {{main|Spin–statistics theorem}}
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| Any subatomic particle, like any particle in the 3-dimensional [[space]] that obeys laws of [[quantum mechanics]], can be either a [[boson]] (that means an integer [[spin (physics)|spin]]) or a [[fermion]] (that means a half-integer spin).
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| === By composition ===
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| The elementary particles of the [[Standard Model]] include:<ref name=IntroSM1>
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| {{Cite book
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| | last = Cottingham | first = W. N.
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| | last2 = Greenwood |first2 =D. A.
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| | year = 2007
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| | title = An introduction to the standard model of particle physics
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| | url = http://books.google.com/?id=Dm36BYq9iu0C&printsec=frontcover
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| | publisher = [[Cambridge University Press]]
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| | page = 1
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| | isbn = 978-0-521-85249-4
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| }}</ref>
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| *Six "[[Flavour (particle physics)|flavors]]" of [[quark]]s: [[Up quark|up]], [[Down quark|down]], [[Bottom quark|bottom]], [[Top quark|top]], [[Strange quark|strange]], and [[Charm quark|charm]];
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| *Six types of [[lepton]]s: [[electron]], [[electron neutrino]], [[muon]], [[muon neutrino]], [[tau (particle)|tau]], [[tau neutrino]];
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| *Twelve [[gauge boson]]s (force carriers): the [[photon]] of [[electromagnetism]], the three [[W and Z bosons]] of the [[weak interaction|weak force]], and the eight [[gluon]]s of the [[strong force]];
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| *The [[Higgs boson]].
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| Various [[Physics beyond the Standard Model|extensions of the Standard Model]] predict the existence of an elementary [[graviton]] particle and [[List of elementary particles#Hypothetical particles|many other elementary particles]].
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| Composite subatomic particles (such as [[proton]]s or atomic [[Atomic nucleus|nuclei]]) are [[bound state]]s of two or more [[elementary particle]]s. For example, a proton is made of two [[up quark]]s and one [[down quark]], while the atomic nucleus of [[helium-4]] is composed of two protons and two [[neutron]]s. Composite particles include all [[hadron]]s: these include [[baryon]]s (such as protons and neutrons) and [[meson]]s (such as [[pion]]s and [[kaon]]s).
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| === By mass ===
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| In [[special relativity]], the [[Mass–energy equivalence|energy of a particle equals its mass times the speed of light squared]] (<math>E = mc^2 \!</math>). That is, [[mass]] can be expressed in terms of [[energy]] and vice versa. If a particle has a [[frame of reference]] where it lies [[rest (physics)|at rest]], then it has a positive [[rest mass]] and is referred to as ''massive''.
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| All composite particles are massive. Baryons (meaning "heavy") tends to have greater mass than mesons (meaning "intermediate"), that in turn tends to be heavier than leptons (meaning "lightweight"), but the heaviest lepton (the [[tau particle]]) is heavier than two lightest flavours of baryons ([[nucleon]]s). It is also certain that any particle with an [[electric charge]] is massive.
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| All [[massless particle]]s (those [[invariant mass]] is zero) are elementary. These are photon and gluon, although the latter cannot be isolated.
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| The question of the masses of [[neutrino]]s is uncertain.
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| ==Other properties==
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| Through the work of [[Albert Einstein]], [[Louis de Broglie]], and many others, current scientific theory holds that ''all'' particles also have a wave nature.<ref>
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| {{Cite book
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| | author = Walter Greiner
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| | year = 2001
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| | title = Quantum Mechanics: An Introduction
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| | url = http://books.google.com/?id=7qCMUfwoQcAC&pg=PA29
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| | page = 29
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| | publisher = [[Springer (publisher)|Springer]]
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| | isbn = 3-540-67458-6
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| }}</ref> This has been verified not only for elementary particles but also for compound particles like atoms and even molecules. In fact, according to traditional formulations of non-relativistic quantum mechanics, wave–particle duality applies to all objects, even macroscopic ones; although wave properties of macroscopic objects cannot be detected due to their small wavelengths.<ref>
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| {{Cite book
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| |author=R. Eisberg and R. Resnick
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| |year=1985
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| |title=Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles
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| |publisher=[[John Wiley & Sons]]
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| |edition=2nd |pages=59–60
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| |isbn=0-471-87373-X
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| |quote=For both large and small wavelengths, both matter and radiation have both particle and wave aspects. [...] But the wave aspects of their motion become more difficult to observe as their wavelengths become shorter. [...] For ordinary macroscopic particles the mass is so large that the momentum is always sufficiently large to make the de Broglie wavelength small enough to be beyond the range of experimental detection, and classical mechanics reigns supreme.
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| }}</ref>
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| Interactions between particles have been scrutinized for many centuries, and a few simple laws underpin how particles behave in collisions and interactions. The most fundamental of these are the laws of [[conservation of energy]] and [[conservation of momentum]], which let us make calculations of particle interactions on scales of magnitude that range from stars to [[quark]]s.<ref>[[Isaac Newton]] (1687). [[Newton's Laws of Motion]] (''[[Philosophiae Naturalis Principia Mathematica]]'')</ref> These are the prerequisite basics of [[Newtonian mechanics]], a series of statements and equations in ''[[Philosophiae Naturalis Principia Mathematica]]'', originally published in 1687.
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| ==Dividing an atom==
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| The negatively-charged electron has a mass equal to {{frac|1836}} of that of a [[hydrogen]] atom. The remainder of the hydrogen atom's mass comes from the positively charged [[proton]]. The [[atomic number]] of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different [[isotope]]s of the same element contain the same number of protons but differing numbers of neutrons. The [[mass number]] of an isotope is the total number of [[nucleon]]s (neutrons and protons collectively).
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| [[Chemistry]] concerns itself with how electron sharing binds atoms into structures such as crystals and [[molecule]]s. [[Nuclear physics]] deals with how protons and neutrons arrange themselves in nuclei. The study of subatomic particles, atoms and molecules, and their structure and interactions, requires [[quantum mechanics]]. Analyzing processes that change the numbers and types of particles requires [[quantum field theory]]. The study of subatomic particles ''per se'' is called [[particle physics]]. The term ''[[high-energy physics]]'' is nearly synonymous to "particle physics" since creation of particles requires high energies: it occurs only as a result of [[cosmic ray]]s, or in [[particle accelerator]]s. [[phenomenology (particle physics)|Particle phenomenology]] systematizes the knowledge about subatomic particles obtained from these experiments.
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| ==History==
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| {{main|History of subatomic physics|Timeline of particle discoveries}}
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| The term "''subatomic'' particle" is largely a [[retronym]] of 1960s made to distinguish a big number of [[baryon]]s and [[meson]]s (that comprise [[hadron]]s) from particles that are now thought to be [[elementary particle|truly elementary]]. Before that hadrons were usually classified as "elementary" because their composition was unknown.
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| A list of important discoveries follows:
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| {| class="wikitable"
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| !Particle
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| !Composition
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| !Theorized
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| !Discovered
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| !Comments
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| |-
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| |[[Electron]] {{subatomic particle|electron}}
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| |elementary ([[lepton]])
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| |[[G. Johnstone Stoney]] (1874)
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| |[[J. J. Thomson]] (1897)
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| |Minimum unit of electrical charge, for which Stoney suggested the name in 1891.<ref>
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| {{Cite book
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| | last = Klemperer | first = Otto
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| | year = 1959
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| | title = Electron Physics: The Physics of the Free Electron
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| | page =
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| | publisher = [[Academic Press]]
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| | isbn =
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| }}</ref>
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| |-
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| |[[alpha particle]] {{subatomic particle|alpha}}
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| |composite (atomic nucleus)
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| |never
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| |[[Ernest Rutherford]] (1899)
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| |-
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| |[[Photon]] {{subatomic particle|photon}}
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| |elementary ([[quantum]])
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| |[[Max Planck]] (1900)
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| |[[Albert Einstein]] (1905)<small><br/> or Ernest Rutherford (1899) as [[Gamma ray|γ rays]]</small>
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| |Necessary to solve the problem of [[black body radiation]] in [[thermodynamics]].
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| |-
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| |[[Proton]] {{subatomic particle|proton}}
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| |composite ([[baryon]])
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| |Long ago
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| |Ernest Rutherford (1918)
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| |The nucleus of {{SimpleNuclide2|hydrogen|1|link=yes}}.
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| |-
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| |[[Neutron]] {{subatomic particle|neutron}}
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| |composite (baryon)
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| |Ernest Rutherford ({{circa}}1918)
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| |[[James Chadwick]] (1932)
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| |The second [[nucleon]].
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| |-
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| |[[Antiparticle]]s
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| |[[Paul Dirac]] (1928)
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| |[[Carl D. Anderson]] ({{subatomic particle|positron|link=yes}}, 1932)
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| |Now explained with [[CPT symmetry]].
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| |-
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| |[[Pion]]s {{subatomic particle|pion}}
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| |composite ([[meson]]s)
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| |[[Hideki Yukawa]] (1935)
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| |[[César Lattes]], [[Giuseppe Occhialini]] (1947) and [[Cecil Powell]]
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| |Explains the [[nuclear force]] between nucleons. The first meson discovered.
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| |-
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| |[[Muon]] {{subatomic particle|muon}}
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| |elementary (lepton)
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| |never
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| |Carl D. Anderson (1936)
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| |Initially mistaken for a meson.
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| |-
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| |[[Kaon]]s {{subatomic particle|kaon}}
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| |composite (mesons)
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| |never
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| |1947
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| |Discovered in [[cosmic ray]]s. The first [[strange particle]].
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| |-
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| |[[Lambda baryon]]s {{subatomic particle|Lambda}}
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| |composite (baryons)
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| |never
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| |[[University of Melbourne]] ({{subatomic particle|Lambda0}}, 1950)<ref>Some sources such as [http://hyperphysics.phy-astr.gsu.edu/Hbase/Particles/quark.html#c4 The Strange Quark] indicate 1947.</ref>
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| |The first [[hyperon]] discovered.
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| |-
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| |[[Neutrino]] {{subatomic particle|neutrino}}
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| |elementary (lepton)
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| |[[Wolfgang Pauli]] (1930), named by [[Enrico Fermi]]
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| |[[Clyde Cowan]], [[Frederick Reines]] ({{subatomic particle|electron neutrino|link=yes}}, 1956)
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| |Solved the problem of energy [[spectrum]] of [[beta decay]].
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| |-
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| |[[Quark]]s<br/>({{subatomic particle|up quark}}, {{subatomic particle|down quark}}, {{subatomic particle|strange quark}})
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| |elementary
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| |[[Murray Gell-Mann]], [[George Zweig]] (1964)
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| | colspan=2 |No particular confirmation event for the [[quark model]].
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| |-
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| |[[charm quark]] {{subatomic particle|charm quark}}
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| |elementary (quark)
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| |1970
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| |1974
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| |-
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| |[[bottom quark]] {{subatomic particle|bottom quark}}
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| |elementary (quark)
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| |1973
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| |1977
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| |-
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| |[[W and Z bosons|Weak gauge bosons]]
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| |elementary (quantum)
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| |[[Sheldon Glashow|Glashow]], [[Steven Weinberg|Weinberg]], [[Abdus Salam|Salam]] (1968)
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| |[[CERN]] (1983)
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| |Properties verified through the 1990s.
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| |-
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| |[[top quark]] {{subatomic particle|top quark}}
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| |elementary (quark)
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| |1973
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| |1995
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| |Does not [[hadronization|hadronize]], but is necessary to complete the Standard Model.
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| |-
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| |[[Higgs boson]]
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| |elementary (quantum)
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| |[[Peter Higgs]] et al. (1964)
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| |CERN (2012)
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| |Thought to be confirmed in 2013.
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| |-
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| |[[Tetraquark]]
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| |composite
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| |?
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| |[[Zc(3900)|Z<sub>c</sub>(3900)]], 2013,<small> to be confirmed as a tetraquark</small>
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| |A new class of hadrons.
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| |-
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| |[[Graviton]]
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| |elementary (quantum)
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| |Albert Einstein (1916)
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| |Not discovered
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| |Interpretation of a [[gravitational wave]] (also hypothetical) as a particle is controversial.
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| |-
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| |[[Magnetic monopole]]
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| |elementary (unclassified)
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| |Paul Dirac (1931)
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| |Not discovered
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| |}
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| ==See also==
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| {{portal|Physics}}
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| {{cmn|3|
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| *''[[Atom: Journey Across the Subatomic Cosmos]]'' (book)
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| *[[CPT invariance]]
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| *[[Dark Matter]]
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| *[[Hot spot effect in subatomic physics]]
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| *[[List of fictional elements, materials, isotopes and atomic particles]]
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| *[[List of particles]]
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| *[[Poincaré symmetry]]
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| *[[Ylem]]
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| }}
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| ==References==
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| {{Reflist|2}}
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| ==Further reading==
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| ;General readers
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| *[[Richard Feynman|Feynman, R.P.]] & [[Steven Weinberg|Weinberg, S.]] (1987). ''Elementary Particles and the Laws of Physics: The 1986 Dirac Memorial Lectures''. Cambridge Univ. Press.
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| *{{Cite book| author=[[Brian Greene]] | title=[[The Elegant Universe]] | publisher=W.W. Norton & Company | year=1999 | isbn=0-393-05858-1}}
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| *Oerter, Robert (2006). ''The Theory of Almost Everything: The Standard Model, the Unsung Triumph of Modern Physics''. Plume.
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| *Schumm, Bruce A. (2004). ''Deep Down Things: The Breathtaking Beauty of Particle Physics''. John Hopkins Univ. Press. ISBN 0-8018-7971-X.
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| *{{Cite book| author=[[Martinus Veltman]] | title=Facts and Mysteries in Elementary Particle Physics | publisher=World Scientific | year=2003 | isbn=981-238-149-X}}
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| ;Textbooks
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| *Coughlan, G. D., J. E. Dodd, and B. M. Gripaios (2006). ''The Ideas of Particle Physics: An Introduction for Scientists'', 3rd ed. Cambridge Univ. Press. An undergraduate text for those not majoring in physics.
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| *{{Cite book| author=Griffiths, David J. | title=Introduction to Elementary Particles | publisher=Wiley, John & Sons, Inc | year=1987 | isbn=0-471-60386-4}}
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| *{{Cite book| author=Kane, Gordon L. | title=Modern Elementary Particle Physics | publisher=Perseus Books | year=1987 | isbn=0-201-11749-5}}
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| ==External links==
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| *[http://particleadventure.org/frameless/standard_model.html particleadventure.org: The Standard Model.]
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| *[http://www.cpepweb.org/cpep_sm_large.html cpepweb.org: Particle chart.]
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| *[http://pdg.lbl.gov/ University of California: Particle Data Group.]
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| *[http://web.mit.edu/redingtn/www/netadv/qft.html Annotated Physics Encyclopædia: Quantum Field Theory.]
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| *[http://jgalvez.home.cern.ch/jgalvez/School/pdf/LM-WeakIteractions.pdf Jose Galvez: Chapter 1 Electrodynamics (pdf).]
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| {{-}}
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| {{Composition}}
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| {{DEFAULTSORT:Subatomic Particle}}
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| [[Category:Subatomic particles| ]]
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| [[Category:Quantum mechanics]]
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