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{{Short description|Type of quark}}
{{distinguish|squark}}
{{Infobox Particle
|bgcolour =
|name = Strange quark
|image = [[File:Strange quark.svg|Strange quark]]
|caption =
|num_types =
|composition = [[Elementary particle]]
|statistics = [[Fermionic]]
|group = [[Quark]]
|generation = Second
|interaction = [[Strong interaction|strong]], [[Weak interaction|weak]], [[electromagnetic force]], [[gravity]]
|particle =
|antiparticle = {{nowrap|Strange antiquark ({{SubatomicParticle|Strange antiquark}})}}
|theorized = [[Murray Gell-Mann]] (1964) [[George Zweig]] (1964)
|discovered = 1947 [[Department of Physics and Astronomy, University of Manchester]], 1968 [[SLAC]]
|symbol = {{SubatomicParticle|Strange quark}}
|mass = {{val|95|+9|-3|ul=MeV/c2}}<ref name="PDG2018">
{{cite journal
|author=M. Tanabashi et al. (Particle Data Group)
|title=Review of Particle Physics
|year=2018
|volume=98
|issue=3
|pages=1–708
|journal=Physical Review D
|pmid=10020536
|url=http://pdglive.lbl.gov/DataBlock.action?node=Q123SM
|bibcode=2018PhRvD..98c0001T
|doi=10.1103/PhysRevD.98.030001 |doi-access=free
|hdl=10044/1/68623 |hdl-access=free
}}</ref>
|decay_time =
|decay_particle = [[Up quark]]
|electric_charge = −{{sfrac|1|3}} [[Elementary charge|''e'']]
|color_charge = Yes
|spin = {{sfrac|1|2}} [[reduced Planck constant|''ħ'']]
|num_spin_states =
|weak_isospin = {{nowrap|[[Chirality (physics)|LH]]: −{{sfrac|1|2}}, [[Chirality (physics)|RH]]: 0}}
|weak_hypercharge= {{nowrap|[[Chirality (physics)|LH]]: {{sfrac|1|3}}, [[Chirality (physics)|RH]]: −{{sfrac|2|3}}}}
}}

The '''strange quark''' or '''s quark''' (from its symbol, s) is the third lightest of all [[quark]]s, a type of [[elementary particle]]. Strange quarks are found in [[subatomic particle]]s called [[hadron]]s. Examples of hadrons containing strange quarks include [[kaon]]s ({{SubatomicParticle|Kaon}}), [[strange D meson]]s ({{SubatomicParticle|Strange D}}), [[sigma baryon]]s ({{SubatomicParticle|Sigma}}), and other [[strange particle]]s.

According to the [[IUPAP]], the symbol '''s''' is the official name, while "strange" is to be considered only as a mnemonic.<ref>{{cite book |last1=Cohen |first1=Richard E. |url=http://iupap.org/wp-content/uploads/2014/05/A4.pdf |title=Symbols, Units, Nomenclature and Fundamental Constants in Physics |last2=Giacomo |first2=Pierre |publisher=IUPAP |edition=2010 |page=12 |access-date=25 March 2017 |archive-url=https://web.archive.org/web/20150318052346/http://iupap.org/wp-content/uploads/2014/05/A4.pdf |archive-date=18 March 2015 }}</ref> The name '''sideways''' has also been used because the s quark (but also the other three remaining quarks) has an [[isospin|''I''{{sub|3}} value]] of 0 while the u ("up") and d ("down") quarks have values of +{{sfrac|1|2}} and −{{sfrac|1|2}} respectively.<ref>{{cite book |last1=McGervey |first1=John D. |title=Introduction to Modern Physics |date=1983 |publisher=Academic Press |location=New York |isbn=978-0-12-483560-3 |page=658 |edition=second |url=https://books.google.com/books?id=2a94GI0-QF0C&q=%22sideways+quark%22&pg=PA658 |access-date=25 March 2017}}</ref>

Along with the [[charm quark]], it is part of the [[generation (physics)|second generation]] of matter. It has an [[electric charge]] of {{sfrac|−|1|3}} [[elementary charge|''e'']] and a [[bare mass]] of {{val|95|+9|-3|ul=MeV/c2}}.<ref name="PDG2018"/> Like all [[quark]]s, the strange quark is an [[elementary particle|elementary]] [[fermion]] with [[Spin (physics)|spin]] [[spin-1/2|{{sfrac|1|2}}]], and experiences all four [[fundamental interaction]]s: [[gravitation]], [[electromagnetism]], [[weak interaction]]s, and [[strong interaction]]s. The [[antiparticle]] of the strange quark is the '''strange antiquark''' (sometimes called ''antistrange quark'' or simply ''antistrange''), which differs from it only in that some of its properties have [[additive inverse|equal magnitude but opposite sign]].

The first [[strange particle]] (a particle containing a strange quark) was discovered by [[George Rochester]] and [[Clifford Butler]] in [[Department of Physics and Astronomy, University of Manchester]] in 1947 ([[kaon]]s), with the existence of the strange quark itself (and that of the [[up quark|up]] and [[down quark]]s) postulated in 1964 by [[Murray Gell-Mann]] and [[George Zweig]] to explain the ''[[Eightfold way (physics)|eightfold way]]'' classification scheme of [[hadron]]s. The first evidence for the existence of quarks came in 1968, in [[deep inelastic scattering]] experiments at the [[Stanford Linear Accelerator Center]]. These experiments confirmed the existence of up and down quarks, and by extension, strange quarks, as they were required to explain the ''eightfold way''.

== History ==
In the beginnings of particle physics (first half of the 20th century), [[hadron]]s such as [[proton]]s, [[neutron]]s and [[pion]]s were thought to be [[elementary particle]]s. However, new hadrons were discovered and the "[[particle zoo]]" grew from a few particles in the early 1930s and 1940s to several dozens of them in the 1950s. Some particles were much longer lived than others; most particles decayed through the [[strong interaction]] and had [[Mean lifetime|lifetime]]s of around 10−23 seconds. When they decayed through the [[weak interaction]]s, they had lifetimes of around 10−10 seconds. While studying these decays, [[Murray Gell-Mann]] (in 1953)<ref>
{{cite journal
|author=M. Gell-Mann
|year=1953
|title=Isotopic Spin and New Unstable Particles
|journal=[[Physical Review]]
|volume=92 |issue= 3|page=833
|doi=10.1103/PhysRev.92.833
|bibcode = 1953PhRv...92..833G |url=https://authors.library.caltech.edu/60471/1/PhysRev.92.833.pdf
}}</ref><ref>
{{cite book |last=Johnson |first=G. |url=https://books.google.com/books?id=iY0buZJ3kRAC&q=Isotopic+Spin+and+New+Unstable+Particles&pg=PA119 |title=Strange Beauty: Murray Gell-Mann and the Revolution in Twentieth-Century Physics |publisher=[[Random House]] |year=2000 |isbn=978-0-679-43764-2 |page=119 |quote=By the end of the summer ... [Gell-Mann] completed his first paper, 'Isotopic Spin and Curious Particles' and send it of to ''Physical Review''. The editors hated the title, so he amended it to 'Strange Particles'. They wouldn't go for that either—never mind that almost everybody used the term—suggesting insteand {{sic}} 'Isotopic Spin and New Unstable Particles'.}}</ref> and [[Kazuhiko Nishijima]] (in 1955)<ref>
{{cite journal |last1=Nishijima |first1=Kazuhiko |year=1955 |title=Charge Independence Theory of V Particles |journal=[[Progress of Theoretical Physics]] |volume=13 |issue=3 |page=285 |bibcode=1955PThPh..13..285N |doi=10.1143/PTP.13.285 |doi-access=free}}</ref> developed the concept of ''[[strangeness]]'' (which Nishijima called ''eta-charge'', after the [[eta meson]] ({{SubatomicParticle|Eta}})) to explain the "strangeness" of the longer-lived particles. The [[Gell-Mann–Nishijima formula]] is the result of these efforts to understand strange decays.

Despite their work, the relationships between each particle and the physical basis behind the strangeness property remained unclear. In 1961, Gell-Mann<ref>
{{cite book |author=Gell-Mann |first=Murray |title=The Eightfold Way |publisher=[[Westview Press]] |year=2000 |isbn=978-0-7382-0299-0 |editor=Ne'eman |editor-first=Y. |page=11 |chapter=The Eightfold Way: A theory of strong interaction symmetry |author-link=Murray Gell-Mann |orig-date=1964}} Original: {{cite journal |author=Gell-Mann |first=Murray |year=1961 |title=The Eightfold Way: A theory of strong interaction symmetry |journal=[[California Institute of Technology]] |publisher=[[Synchrotron Laboratory]] Report CTSL-20 }}</ref> and [[Yuval Ne'eman]]<ref>
{{cite book
|author=Y. Ne'eman
|year=2000 |orig-date=1964
|chapter=Derivation of strong interactions from gauge invariance
|editor=M. Gell-Mann, Y. Ne'eman
|title=The Eightfold Way
|publisher=[[Westview Press]]
|isbn=978-0-7382-0299-0
}} Original {{cite journal
|author=Y. Ne'eman
|year=1961
|title=Derivation of strong interactions from gauge invariance
|journal=[[Nuclear Physics (journal)|Nuclear Physics]]
|volume=26 |page=222
|doi=10.1016/0029-5582(61)90134-1
|bibcode = 1961NucPh..26..222N
|issue=2 }}</ref> independently proposed a hadron classification scheme called the [[Eightfold way (physics)|eightfold way]], also known as [[SU(3)]] [[flavor symmetry]]. This ordered hadrons into [[isospin|isospin multiplet]]s. The physical basis behind both isospin and strangeness was only explained in 1964, when Gell-Mann<ref name="Gell-Man1964">
{{cite journal |author=Gell-Mann |first=Murray |author-link=Murray Gell-Mann |year=1964 |title=A Schematic Model of Baryons and Mesons |journal=[[Physics Letters]] |volume=8 |issue=3 |pages=214–215 |bibcode=1964PhL.....8..214G |doi=10.1016/S0031-9163(64)92001-3}}</ref> and [[George Zweig]]<ref name="Zweig1964a">
{{cite journal |author=Zweig |first=G. |year=1964 |title=An SU(3) Model for Strong Interaction Symmetry and its Breaking |journal=CERN Report No.8181/Th 8419}}</ref><ref name="Zweig1964b">
{{cite journal |author=Zweig |first=G. |year=1964 |title=An SU(3) Model for Strong Interaction Symmetry and its Breaking: II |journal=CERN Report No.8419/Th 8412}}</ref> independently proposed the [[quark model]], which at that time consisted only of the up, down, and strange quarks.<ref name="Carithers">
{{cite journal |author=Carithers |first1=B. |last2=Grannis |first2=P. |year=1995 |title=Discovery of the Top Quark |url=http://www.slac.stanford.edu/pubs/beamline/25/3/25-3-carithers.pdf |journal=[[Beam Line (journal)|Beam Line]] |volume=25 |issue=3 |pages=4–16 |access-date=2008-09-23}}</ref> Up and down quarks were the carriers of isospin, while the strange quark carried strangeness. While the quark model explained the ''eightfold way'', no direct evidence of the existence of quarks was found until 1968 at the [[Stanford Linear Accelerator Center]].<ref name="Bloom">
{{cite journal |last1=Bloom |first1=E. D. |last2=Coward |first2=D. |last3=Destaebler |first3=H. |last4=Drees |first4=J. |last5=Miller |first5=G. |last6=Mo |first6=L. |last7=Taylor |first7=R. |last8=Breidenbach |first8=M. |last9=Friedman |first9=J. |last10=Hartmann |first10=G. |last11=Kendall |first11=H. |display-authors=2 |year=1969 |title=High-Energy Inelastic ''e''–''p'' Scattering at 6° and 10° |journal=[[Physical Review Letters]] |volume=23 |issue=16 |pages=930–934 |bibcode=1969PhRvL..23..930B |doi=10.1103/PhysRevLett.23.930 |doi-access=free}}</ref><ref name="Breidenbach">
{{cite journal |author=Breidenbach |first1=M. |last2=Friedman |first2=J. |last3=Kendall |first3=H. |last4=Bloom |first4=E. |last5=Coward |first5=D. |last6=Destaebler |first6=H. |last7=Drees |first7=J. |last8=Mo |first8=L. |last9=Taylor |first9=R. |display-authors=2 |year=1969 |title=Observed Behavior of Highly Inelastic Electron–Proton Scattering |journal=[[Physical Review Letters]] |volume=23 |issue=16 |pages=935–939 |bibcode=1969PhRvL..23..935B |doi=10.1103/PhysRevLett.23.935 |osti=1444731 |s2cid=2575595}}</ref> [[Deep inelastic scattering]] experiments indicated that [[proton]]s had substructure, and that protons made of three more-fundamental particles explained the data (thus confirming the [[quark model]]).<ref>
{{cite web |author=Friedman |first=J. I. |title=The Road to the Nobel Prize |url=http://www.hueuni.edu.vn/hueuni/en/news_detail.php?NewsID=1606&PHPSESSID=909807ffc5b9c0288cc8d137ff063c72 |archive-url=https://web.archive.org/web/20081225093044/http://www.hueuni.edu.vn/hueuni/en/news_detail.php?NewsID=1606&PHPSESSID=909807ffc5b9c0288cc8d137ff063c72 |archive-date=25 December 2008 |access-date=29 September 2008 |publisher=[[Hue University]]}}</ref>

At first people were reluctant to identify the three-bodies as quarks, instead preferring [[Richard Feynman]]'s [[Parton (particle physics)|parton]] description,<ref>
{{cite journal |author=Feynman |first=R. P. |year=1969 |title=Very High-Energy Collisions of Hadrons |url=http://authors.library.caltech.edu/3871/1/FEYprl69.pdf |journal=[[Physical Review Letters]] |volume=23 |issue=24 |pages=1415–1417 |bibcode=1969PhRvL..23.1415F |doi=10.1103/PhysRevLett.23.1415}}</ref><ref>
{{cite journal |author=Kretzer |first1=S. |last2=Lai |first2=H. |last3=Olness |first3=Fredrick |last4=Tung |first4=W. |display-authors=2 |year=2004 |title=CTEQ6 Parton Distributions with Heavy Quark Mass Effects |journal=[[Physical Review D]] |volume=69 |issue=11 |article-number=114005 |arxiv=hep-th/0307022 |bibcode=2004PhRvD..69k4005K |doi=10.1103/PhysRevD.69.114005 |s2cid=119379329}}</ref><ref name="Griffiths">
{{cite book |author=Griffiths |first=D. J. |url=https://archive.org/details/introductiontoel00grif_077 |title=Introduction to Elementary Particles |publisher=[[John Wiley & Sons]] |year=1987 |isbn=978-0-471-60386-3 |page=[https://archive.org/details/introductiontoel00grif_077/page/n49 42] |url-access=limited}}</ref> but over time the quark theory became accepted (see ''[[November Revolution (physics)|November Revolution]]'').<ref>
{{cite book |author=Peskin |first1=M. E. |url=https://archive.org/details/introductiontoqu0000pesk |title=An introduction to quantum field theory |last2=Schroeder |first2=D. V. |publisher=[[Addison–Wesley]] |year=1995 |isbn=978-0-201-50397-5 |page=[https://archive.org/details/introductiontoqu0000pesk/page/556 556] |url-access=registration}}</ref>

== See also ==
* [[Strangeness]]
* [[Quark model]]
* [[Strange matter]]
* [[Strangeness production]]
* [[Strangelet]]
* [[Strange star]]

== References ==
{{reflist|2}}

== Further reading ==
* {{cite web
|author=R. Nave
|title=Quarks
|url=http://hyperphysics.phy-astr.gsu.edu/hbase/Particles/quark.html
|work=[[HyperPhysics]]
|publisher=[[Georgia State University]], Department of Physics and Astronomy
|access-date=2008-06-29
}}
* {{cite book
|author=A. Pickering
|title=Constructing Quarks
|pages=114–125
|publisher=[[University of Chicago Press]]
|year=1984
|isbn=978-0-226-66799-7
}}

{{Particles}}
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{{DEFAULTSORT:Strange Quark}}
[[Category:Strange quark| ]]
[[Category:Quarks]]
[[Category:Elementary particles]]

Strange quark - Revision history

imported>Monkbot: Monkbot/task 21: Replace page(s) with article-number;