Strange quark

{{Infobox Particle

|bgcolour =

|name = Strange quark

|image = Strange quark

|caption =

|num_types =

|composition = Elementary particle

|statistics = Fermionic

|group = Quark

|generation = Second

|interaction = strong, 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}}

{{cite journal

|author=M. Tanabashi et al. (Particle Data Group)

|title=Review of Particle Physics

|year= 2018

|doi=10.1103/PhysRevD.98.030001

|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-access=free

|hdl=10044/1/68623

|hdl-access=free

}}

|decay_time =

|decay_particle = Up quark

|electric_charge = −{{sfrac|1|3}} e

|color_charge = Yes

|spin = {{sfrac|1|2}} ħ

|num_spin_states =

|weak_isospin = {{nowrap|LH: −{{sfrac|1|2}}, RH: 0}}

|weak_hypercharge= {{nowrap|LH: {{sfrac|1|3}}, RH: −{{sfrac|2|3}}}}

}}

The strange quark or s quark (from its symbol, s) is the third lightest of all quarks, a type of elementary particle. Strange quarks are found in subatomic particles called hadrons. Examples of hadrons containing strange quarks include kaons ({{SubatomicParticle|Kaon}}), strange D mesons ({{SubatomicParticle|Strange D}}), Sigma baryons ({{SubatomicParticle|Sigma}}), and other strange particles.

According to the IUPAP, the symbol s is the official name, while "strange" is to be considered only as a mnemonic.{{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 |url-status=dead}} The name sideways has also been used because the s quark (but also the other three remaining quarks) has an isospin of 0 while the u ("up") and d ("down") quarks have values of +{{sfrac|1|2}} and −{{sfrac|1|2}} respectively.{{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}}

Along with the charm quark, it is part of the second generation of matter. It has an electric charge of {{sfrac|−|1|3}} e and a bare mass of {{val|95|+9|-3|ul=MeV/c2}}. Like all quarks, the strange quark is an elementary fermion with spin spin-1/2, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and strong interactions. 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 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 (kaons), with the existence of the strange quark itself (and that of the up and down quarks) postulated in 1964 by Murray Gell-Mann and George Zweig to explain the eightfold way classification scheme of hadrons. 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), hadrons such as protons, neutrons and pions were thought to be elementary particles. 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 lifetimes of around 10⁻²³ seconds. When they decayed through the weak interactions, they had lifetimes of around 10⁻¹⁰ seconds. While studying these decays, Murray Gell-Mann (in 1953)

{{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

}}

{{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'.}} and Kazuhiko Nishijima (in 1955)

{{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}} 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

{{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 }} and Yuval Ne'eman

{{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

}}
Original {{cite journal

|author=Y. Ne'eman

|year=1961

|title=Derivation of strong interactions from gauge invariance

|journal=Nuclear Physics

|volume=26 |page=222

|doi=10.1016/0029-5582(61)90134-1

|bibcode = 1961NucPh..26..222N

|issue=2 }} independently proposed a hadron classification scheme called the eightfold way, also known as SU(3) flavor symmetry. This ordered hadrons into isospin multiplets. The physical basis behind both isospin and strangeness was only explained in 1964, when Gell-Mann

{{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}} and George Zweig

{{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}}

{{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}} independently proposed the quark model, which at that time consisted only of the up, down, and strange quarks.

{{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 |volume=25 |issue=3 |pages=4–16 |access-date=2008-09-23}} 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.

{{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}}

{{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}} Deep inelastic scattering experiments indicated that protons had substructure, and that protons made of three more-fundamental particles explained the data (thus confirming the quark model).

{{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}}

At first people were reluctant to identify the three-bodies as quarks, instead preferring Richard Feynman's parton description,

{{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}}

{{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}}

{{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}} but over time the quark theory became accepted (see November Revolution).

{{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}}

Strange quark

History

See also

References

Further reading