View source for Hyperon

{{Short description|Type of strange baryon}}
{{Distinguish|Hyperion (disambiguation)}}
{{Standard model of particle physics}}
In [[particle physics]], a '''hyperon''' is any [[baryon]] containing one or more [[strange quark]]s, but no [[charm quark|charm]], [[bottom quark|bottom]], or [[top quark]]s.<ref>{{cite book |last1=Greiner |first1=Walter |title=An Advanced Course in Modern Nuclear Physics |volume=581 |pages=316–342 |editor1-last=Arias |editor1-first=J.M. |editor2-last=Lozano |editor2-first=M. |ref=Greiner2001 |chapter=Structure of vacuum and elementary matter: from superheavies via hypermatter to antimatter.|doi=10.1007/3-540-44620-6_11 |series=Lecture Notes in Physics |year=2001 |isbn=978-3-540-42409-3 }}</ref> This form of matter may exist in a stable form within the core of some [[neutron star]]s.<ref name=SchaffnerBielich2002>{{citation |title=Phase Transition to Hyperon Matter in Neutron Stars |last1=Schaffner-Bielich |first1=Jürgen |last2=Hanauske |first2=Matthias |last3=Stöcker |first3=Horst |last4=Greiner |first4=Walter |journal=Physical Review Letters |display-authors=1 |volume=89 |issue=17 |article-number=171101 |id=171101 |year=2002 |postscript= |doi=10.1103/PhysRevLett.89.171101 |pmid=12398654 |bibcode=2002PhRvL..89q1101S |arxiv=astro-ph/0005490| s2cid=18759347 }}</ref> Hyperons are sometimes generically represented by the symbol '''Y'''.<ref>{{cite journal |last1=Tolos |first1=L. |last2=Fabbietti |first2=L. |title=Strangeness in nuclei and neutron stars |journal=Progress in Particle and Nuclear Physics |date=May 2020 |volume=112 |page=41 |article-number=103770 |doi=10.1016/j.ppnp.2020.103770|arxiv=2002.09223 |bibcode=2020PrPNP.11203770T |s2cid=211252559 }}</ref>

== History and research ==
The first research into hyperons happened in the 1950s and spurred physicists on to the creation of an organized classification of particles.

The term was coined by French physicist [[Louis Leprince-Ringuet]] in 1953,<ref>{{cite journal |last1=Degrange |first1=Bernard |last2=Fontaine |first2=Gérard |last3=Fleury |first3=Patrick |date=2013 |title=Tracking Louis Leprince-Ringuet's contributions to cosmic-ray physics |url=http://physicstoday.scitation.org/doi/10.1063/PT.3.1989 |journal=Physics Today |language=en |volume=66 |issue=6|page=8 |doi=10.1063/PT.3.1989 |bibcode=2013PhT....66f...8D |issn=0031-9228|url-access=subscription }}</ref><ref>{{cite conference |last=Ravel|first=Olivier|date=2013|editor-last=Ormes |editor-first=Jonathan F.|title=Early cosmic ray research in France|url=https://hal.archives-ouvertes.fr/hal-00841758 |conference=Centenary Symposium 2012: Discovery of Cosmic Rays|series=AIP Conference Proceedings |volume=1516|location=Denver, United States |publisher=American Institute of Physics |pages=67–71|doi=10.1063/1.4792542|bibcode=2013AIPC.1516...67R|isbn=978-0-7354-1137-1}}</ref> and announced for the first time at the cosmic ray conference at [[Bagnères de Bigorre]] in July of that year, agreed upon by Leprince-Ringuet, [[Bruno Rossi]], [[C. F. Powell|C.F. Powell]], [[William Bache Fretter|William B. Fretter]] and [[Bernard Peters]].<ref>{{cite journal |title = The 1953 Cosmic Ray Conference at Bagnères de Bigorre: the Birth of Sub Atomic Physics |author = J.W. Cronin |doi = 10.1140/epjh/e2011-20014-4 |year = 2011 |volume = 36 |pages = 183–201 |journal = The European Physical Journal H| issue = 2 |arxiv = 1111.5338 |bibcode = 2011EPJH...36..183C |s2cid = 119105540 }} See in particular Fig. 5.</ref>

Today, research in this area is carried out on data taken at many facilities around the world, including [[CERN]], [[Fermilab]], [[SLAC]], [[Thomas Jefferson National Accelerator Facility|JLAB]], [[Brookhaven National Laboratory]], [[KEK]], [[GSI Helmholtz Centre for Heavy Ion Research|GSI]] and others. Physics topics include searches for [[CP violation]], measurements of [[Spin (physics)|spin]], studies of [[excited state]]s (commonly referred to as ''spectroscopy''), and hunts for exotic forms such as [[pentaquark]]s and [[dibaryon]]s.

== Properties and behavior ==
[[Image:Baryon decuplet.svg|230px|thumb|A combination of three u, d or s-quarks with a total spin of 3/2 form the so-called '''baryon decuplet'''. The lower six are hyperons.]]
Being baryons, all hyperons are [[fermion]]s. That is, they have [[half-integer]] [[Spin (physics)|spin]] and obey [[Fermi–Dirac statistics]]. Hyperons all interact via the [[strong nuclear force]], making them types of [[hadron]]. They are composed of three light [[quark]]s, at least one of which is a [[strange quark]], which makes them strange baryons.

Excited hyperon resonances and ground-state hyperons with a '*' included in their notation decay via the [[strong interaction]]. For {{subatomic particle|omega-|link=yes}} as well as the lighter hyperons this decay mode is not possible given the particle masses and the conservation of [[Flavour (particle physics)|flavor]] and [[isospin]] necessary in strong interactions. Instead, these decay [[weak interaction|weakly]] with non-conserved [[parity (physics)|parity]]. An exception to this is the {{subatomic particle|sigma0|link=yes}} which decays [[Electromagnetism|electromagnetically]] into [[Lambda baryon|Λ]] on account of carrying the same flavor quantum numbers. The type of interaction through which these decays occur determine the average lifetime, which is why weakly decaying hyperons are significantly more long-lived than those that decay through strong or electromagnetic interactions.<ref>{{cite book |last1=Martin |first1=B. R. |title=Particle physics |date=2017 |location=Chichester, West Sussex, United Kingdom |isbn=978-1-118-91190-7 |edition=Fourth}}</ref>

==List==
{| class="wikitable sortable"
|+Hyperons
|-
! class=unsortable | Particle
! Symbol 
! Makeup 
! [[Rest mass]] {{br}}{{bracket|[[electron volt|MeV]]/[[speed of light|''c'']]<sup>2</sup>}}
! [[Isospin]], {{br}}''I''
! [[Spin (physics)|Spin]], [[parity (physics)|parity]],{{br}}[[Spin (physics)|''J'']]<sup>[[parity (physics)|P]]</sup>
! [[charge (physics)|''Q'']] {{br}}{{bracket|''e''}}
! [[strangeness|''S'']]
! [[charm (quantum number)|''C'']]
! [[bottomness|''B''′]]
! [[Mean lifetime]] {{br}}{{bracket|[[second|s]]}}
! class=unsortable | Commonly {{br}}decays to 
|-
| [[Lambda baryon|Lambda]]<ref>{{cite web |url=http://pdg.lbl.gov/2007/listings/s018.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Lambda |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175117/http://pdg.lbl.gov/2007/listings/s018.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Lambda0}}
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1 115.683(6)
| 0
| {{sfrac|1|2}}<sup>+</sup>
| 0
| −1
| 0
| 0
| {{val|2.60|e=-10}}{{px2}}<ref name=ParticlePhysicsOverview>{{cite web|url=http://filer.case.edu/sjr16/advanced/extras_particlephys.html |title=Physics Particle Overview – Baryons |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080228011850/http://filer.case.edu/sjr16/advanced/extras_particlephys.html |archive-date=2008-02-28 }}</ref>
| {{nowrap|{{SubatomicParticle|link=yes|Proton+}} + {{SubatomicParticle|link=yes|Pion-}}}} or {{br}} {{nowrap|{{SubatomicParticle|link=yes|Neutron0}} + {{SubatomicParticle|link=yes|Pion0}}}}
|-
| [[Lambda baryon|Lambda]] resonance<ref>{{cite web |url=http://pdg.lbl.gov/2007/listings/s018.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Lambda |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175117/http://pdg.lbl.gov/2007/listings/s018.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Lambda}}(1405)
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| {{val|1405.1|+1.3|-1.0}}
| 0
| {{sfrac|1|2}}<sup>−</sup>
| 0
| −1
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|link=yes|Sigma}} + {{SubatomicParticle|link=yes|Pion}}}} 
|-
| [[Lambda baryon|Lambda]] resonance<ref>{{cite web |url=http://pdg.lbl.gov/2007/listings/s018.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Lambda |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175117/http://pdg.lbl.gov/2007/listings/s018.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Lambda}}(1520)
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1 519(1)
| 0
| {{sfrac|3|2}}<sup>−</sup>
| 0
| −1
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|link=yes|Nucleon}} + {{SubatomicParticle|link=yes|Kaon}}}} or {{nowrap|{{SubatomicParticle|link=yes|Sigma}} + {{SubatomicParticle|link=yes|pion}}}} or {{nowrap|{{SubatomicParticle|link=yes|Lambda}} + 2{{SubatomicParticle|link=yes|pion}}}} 
|-
| [[Sigma baryon|Sigma]]<ref name="PDGSigma+">{{cite web |url=http://pdg.lbl.gov/2007/listings/s019.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Sigma+ |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175104/http://pdg.lbl.gov/2007/listings/s019.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Sigma+}}
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;189.37(7)
| 1
| {{sfrac|1|2}}<sup>+</sup>
| +1
| −1
| 0
| 0
| {{val|8.018|0.026|e=-11}}
| {{nowrap|{{SubatomicParticle|link=yes|Proton+}} + {{SubatomicParticle|link=yes|Pion0}}}} or {{br}}{{nowrap|{{SubatomicParticle|link=yes|Neutron0}} + {{SubatomicParticle|link=yes|Pion+}}}}
|-
| [[Sigma baryon|Sigma]]<ref name=PDGSigma0>{{cite web |url=http://pdg.lbl.gov/2007/listings/s021.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Sigma0 |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175105/http://pdg.lbl.gov/2007/listings/s021.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Sigma0}}
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;192.642(24)
| 1
| {{sfrac|1|2}}<sup>+</sup>
| 0
| −1
| 0
| 0
| {{val|7.4|0.7|e=-20}}
| {{nowrap|{{SubatomicParticle|link=yes|Lambda0}} + {{SubatomicParticle|link=yes|Photon}}}}
|-
| [[Sigma baryon|Sigma]]<ref name=PDGSigma->{{cite web |url=http://pdg.lbl.gov/2007/listings/s020.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Sigma- |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175103/http://pdg.lbl.gov/2007/listings/s020.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Sigma-}}
| {{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;197.449(30)
| 1
| {{sfrac|1|2}}<sup>+</sup>
| −1
| −1
| 0
| 0
| {{val|1.479|0.011|e=-10}}
| {{nowrap|{{SubatomicParticle|link=yes|Neutron0}} + {{SubatomicParticle|link=yes|Pion-}}}}
|-
| [[Sigma baryon|Sigma]] resonance<ref name=PDGSigma(1385)>{{cite web |url=http://pdg.lbl.gov/2007/listings/b043.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Sigma(1385) |access-date=2008-04-20 |archive-url=https://web.archive.org/web/20080910175104/http://pdg.lbl.gov/2007/listings/b043.pdf |archive-date=2008-09-10 }}</ref>
| {{SubatomicParticle|link=yes|Sigma*+}}(1385)
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;382.8(4)
| 1
| {{sfrac|3|2}}<sup>+</sup>
| +1
| −1
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|Lambda}} + {{SubatomicParticle|Pion}}}} or {{br}} {{nowrap|{{SubatomicParticle|Sigma}} + {{SubatomicParticle|Pion}}}}
|-
| [[Sigma baryon|Sigma]] resonance<ref name=PDGSigma(1385)/>
| {{SubatomicParticle|link=yes|Sigma*0}}(1385)
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| {{val|1383.7|(1.0)}}
| 1
| {{sfrac|3|2}}<sup>+</sup>
| 0
| −1
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|Lambda}} + {{SubatomicParticle|Pion}}}} or {{br}} {{nowrap|{{SubatomicParticle|Sigma}} + {{SubatomicParticle|Pion}}}}
|-
| [[Sigma baryon|Sigma]] resonance<ref name=PDGSigma(1385)/>
| {{SubatomicParticle|link=yes|Sigma*-}}(1385)
| {{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;387.2(5)
| 1
| {{sfrac|3|2}}<sup>+</sup>
| −1
| −1
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|Lambda}} + {{SubatomicParticle|Pion}}}} or {{br}} {{nowrap|{{SubatomicParticle|Sigma}} + {{SubatomicParticle|Pion}}}}
|- 
| [[Xi baryon|Xi]]<ref name=PDGXi0>{{cite web |url=http://pdg.lbl.gov/2007/listings/s023.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Xi0|access-date=2008-04-20 }}</ref>
| {{SubatomicParticle|link=yes|Xi0}}
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;314.86(20)
| {{sfrac|1|2}}
| {{sfrac|1|2}}<sup>+</sup>
| 0
| −2
| 0
| 0
| {{val|2.90|0.09|e=-10}}
| {{nowrap|{{SubatomicParticle|link=yes|Lambda0}} + {{SubatomicParticle|link=yes|Pion0}}}}
|-
| [[Xi baryon|Xi]]<ref name=PDGXi->{{cite web |url=http://pdg.lbl.gov/2007/listings/s022.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Xi-|access-date=2008-04-20 }}</ref>
| {{SubatomicParticle|link=yes|Xi-}}
| {{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;321.71(7)
| {{sfrac|1|2}}
| {{sfrac|1|2}}<sup>+</sup>
| −1
| −2
| 0
| 0
| {{val|1.639|0.015|e=-10}}
| {{nowrap|{{SubatomicParticle|link=yes|Lambda0}} + {{SubatomicParticle|link=yes|Pion-}}}}
|-
| [[Xi baryon|Xi]] resonance<ref name=PDGXi(1530)>{{cite web |url=http://pdg.lbl.gov/2007/listings/b049.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Xi(1530)|access-date=2008-04-20 }}</ref>
| {{SubatomicParticle|link=yes|Xi*0}}(1530)
| {{SubatomicParticle|link=yes|Up quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;531.80(32)
| {{sfrac|1|2}}
| {{sfrac|3|2}}<sup>+</sup>
| 0
| −2
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|link=yes|Xi}} + {{SubatomicParticle|link=yes|Pion}}}}
|-
| [[Xi baryon|Xi]] resonance<ref name=PDGXi(1530)/>
| {{SubatomicParticle|link=yes|Xi*-}}(1530)
| {{SubatomicParticle|link=yes|Down quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;535.0(6)
| {{sfrac|1|2}}
| {{sfrac|3|2}}<sup>+</sup>
| −1
| −2
| 0
| 0
| 
| {{nowrap|{{SubatomicParticle|link=yes|Xi}} + {{SubatomicParticle|link=yes|Pion}}}}
|-
| [[Omega baryon|Omega]]<ref name=PDGOmega->{{cite web |url=http://pdg.lbl.gov/2007/listings/s024.pdf |title=Particle Data Groups: 2006 Review of Particle Physics – Omega-|access-date=2008-04-20 }}</ref>
| {{SubatomicParticle|link=yes|Omega-}}
| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}
| 1&nbsp;672.45(29)
| 0 
| {{sfrac|3|2}}<sup>+</sup>
| −1
| −3
| 0
| 0
| {{val|8.21|0.11|e=-11}}
| {{nowrap|{{SubatomicParticle|link=yes|Lambda0}} + {{SubatomicParticle|link=yes|Kaon-}}}} or {{br}} {{nowrap|{{SubatomicParticle|link=yes|Xi0}} + {{SubatomicParticle|link=yes|Pion-}}}} or {{br}} {{nowrap|{{SubatomicParticle|link=yes|Xi-}} + {{SubatomicParticle|link=yes|Pion0}}}}
|}

Notes:
* Since [[strangeness]] is conserved by the [[strong interaction]]s, some ground-state hyperons cannot decay strongly. However, they do participate in strong interactions.
* {{SubatomicParticle|Lambda0}} may also decay on rare occurrences via these processes:
*: {{SubatomicParticle|Lambda0}} → {{SubatomicParticle|Proton+}} + {{SubatomicParticle|Electron}} + {{SubatomicParticle|Electron antineutrino}}
*: {{SubatomicParticle|Lambda0}} → {{SubatomicParticle|Proton+}} + {{SubatomicParticle|Muon}} + {{SubatomicParticle|Muon antineutrino}}
* {{SubatomicParticle|Xi0}} and {{SubatomicParticle|Xi-}} are also known as "cascade" hyperons, since they go through a two-step cascading decay into a [[nucleon]].
* The {{SubatomicParticle|Omega-}} has a [[baryon number]] of +1 and [[hypercharge]] of −2, giving it strangeness of −3. It takes multiple flavor-changing [[weak interaction|weak decays]] for it to decay into a proton or neutron. [[Murray Gell-Mann]]'s and [[Yuval Ne'eman]]'s [[Special unitary group|SU(3)]] model (sometimes called the [[Eightfold way (physics)|Eightfold Way]]) predicted this hyperon's existence, mass and that it will only undergo weak decay processes. Experimental evidence for its existence was discovered in 1964 at [[Brookhaven National Laboratory]]. Further examples of its formation and observation using [[particle accelerator]]s confirmed the SU(3) model.

== See also ==
{{Wiktionary|hyperon}}
{{cols}}
* [[Delta baryon]]
* [[Hypernucleus]]
* [[Strangelet]]
* [[List of baryons]]
* [[List of particles]]
* [[Physics portal]]
* [[Timeline of particle discoveries]]
{{colend}}

== References ==
{{reflist}}
* {{cite book |first1=Henry |last1=Semat |first2=John R. |last2=Albright |year=1984 |title=Introduction to Atomic and Nuclear Physics |publisher=[[Chapman and Hall]] |isbn=0-412-15670-9}}

{{particles}}
{{Authority control}}

[[Category:Baryons]]
[[Category:Exotic matter]]
[[Category:Strange quark]]