Editing Strange quark (section)

== 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<sup>−23</sup> seconds. When they decayed through the [[weak interaction]]s, they had lifetimes of around 10<sup>−10</sup> 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}}<br /> 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-year=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
}}<br/>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 |url-status=dead |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 |page=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>