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Omega baryon

{{Short description|Subatomic hadron particle}}

{{redirect|Omega particle|usage of the term in Star Trek|The Omega Directive}}

{{distinguish|Omega meson}}

{{Use dmy dates|date=February 2021}}

Image:Omega Baryon.svg trace of the first observed Ω baryon event at Brookhaven National Laboratory, adapted from original tracing. The tracks of neutral particles (dashed lines) are not visible in the bubble chamber. The collision of a K− meson with a proton creates an Ω−, a K0 and a K+. The Ω− decays into a π− and a Ξ0, which in turn decays into a Λ0 and a π0. The Λ0 decays into a proton and a π−. The π0, invisible due to its short lifetime, decays into two photons (γ), which in turn each create an electron-positron pair.]]

Omega baryons (often called simply omega particles) are a family of subatomic hadrons which are represented by the symbol {{SubatomicParticle|Omega}} and are either charge neutral or have a +2, +1 or −1 elementary charge. Additionally, they contain no up or down quarks.{{cite web | author=Particle Data Group | author-link=Particle Data Group |url=http://pdg.lbl.gov/2011/reviews/rpp2011-rev-naming-scheme-hadrons.pdf |title= 2010 Review of Particle Physics – Naming scheme for hadrons |access-date=2011-12-26 }} Omega baryons containing top quarks are also not expected to be observed. This is because the Standard Model predicts the mean lifetime of top quarks to be roughly {{val|5|e=-25|u=s}},

{{cite journal

|author=A. Quadt

|year=2006

|title=Top quark physics at hadron colliders

|journal=European Physical Journal C

|volume=48 |issue=3 |pages=835–1000

|bibcode = 2006EPJC...48..835Q

|doi=10.1140/epjc/s2006-02631-6

|s2cid=121887478

|url=https://cds.cern.ch/record/1339554

}} which is about a twentieth of the timescale necessary for the strong interactions required for hadronization, the process by which hadrons form from quarks and gluons.

The first omega baryon was the {{SubatomicParticle|Omega-}}, it was made of three strange quarks, and was discovered in 1964.

{{cite journal

|author=V. E. Barnes|year=1964

|title=Observation of a Hyperon with Strangeness Minus Three

|url=http://teachers.web.cern.ch/teachers/archiv/HST2001/bubblechambers/omegaminus.pdf

|journal=Physical Review Letters

|volume=12 |issue=8 |page=204

|bibcode = 1964PhRvL..12..204B

|doi = 10.1103/PhysRevLett.12.204

|osti=12491965

|display-authors=etal}} The discovery was a great triumph in the study of quarks, since it was found only after its existence, mass, and decay products had been predicted in 1961 by the American physicist Murray Gell-Mann and, independently, by the Israeli physicist Yuval Ne'eman. Besides the {{SubatomicParticle|Omega-}}, a charmed omega particle ({{SubatomicParticle|Charmed Omega0}}) was discovered in 1985, in which a strange quark is replaced by a charm quark. The {{SubatomicParticle|Omega-}} decays only via the weak interaction and has therefore a relatively long lifetime.

{{cite web

|author=R. Nave

|title=The Omega baryon

|url=http://hyperphysics.phy-astr.gsu.edu/hbase/particles/omega.html#c1

|website=HyperPhysics

|access-date=2009-11-26

}} Spin (J) and parity (P) values for unobserved baryons are predicted by the quark model.{{Cite journal|date=1994-01-01|title=Heavy baryons |journal=Progress in Particle and Nuclear Physics |volume=33|pages=787–868|doi=10.1016/0146-6410(94)90053-1 |last1=Körner|first1=J.G|last2=Krämer|first2=M|last3=Pirjol|first3=D|arxiv=hep-ph/9406359 |bibcode=1994PrPNP..33..787K|s2cid=118931787 }}

Since omega baryons do not have any up or down quarks, they all have isospin 0.

Omega baryons

File:Quark structure omega.svg

class="wikitable sortable"

|+Omega

class=unsortable|Particle

! Symbol

! Quark
content

! Rest mass
(MeV/c2)

! JP

! Q
(e)

! S

! C

! {{nowrap|B'}}

! Mean lifetime
(s)

! class=unsortable|Decays to

Omega{{cite web |author=Particle Data Group |author-link=Particle Data Group |url=http://pdg.lbl.gov/2007/listings/s024.pdf |title= 2006 Review of Particle Physics – {{SubatomicParticle|Omega-}} |access-date=2008-04-20 }}

| {{SubatomicParticle|Omega-}}

| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}

| {{val|1672.45|0.29}}

| {{sfrac|3|2}}+

| −1

| −3

| 0

| 0

| {{val|8.21|0.11|e=-11}}

| {{nowrap|{{SubatomicParticle|link=yes|Lambda0}} + {{SubatomicParticle|link=yes|Kaon-}}}} or
{{nowrap|{{SubatomicParticle|link=yes|Xi0}} + {{SubatomicParticle|link=yes|Pion-}}}} or
{{nowrap|{{SubatomicParticle|link=yes|Xi-}} + {{SubatomicParticle|link=yes|Pion0}}}}

Charmed omega{{cite web |author=Particle Data Group |author-link=Particle Data Group |url=http://pdg.lbl.gov/2018/listings/rpp2018-list-omegac-zero.pdf |title={{SubatomicParticle|Charmed omega0}} listing – {{SubatomicParticle|Charmed Omega0}}|access-date=13 August 2018 }}

| {{SubatomicParticle|Charmed Omega0}}

| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Charm quark}}

| {{val|2697.5|2.6}}

| {{sfrac|1|2}}+

| 0

| −2

| +1

| 0

| {{val|268|24|e=-15}}

| See [https://pdg.lbl.gov/2022/listings/contents_listings.html {{SubatomicParticle|Charmed omega0}} Decay Modes]

Bottom omega

| {{SubatomicParticle|Bottom Omega-}}

| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Bottom quark}}

| {{val|6054.4|6.8}}

| {{sfrac|1|2}}+

| −1

| −2

| 0

| −1

|{{val|1.13|0.53|e=-12}}

|{{nowrap|{{SubatomicParticle|Omega-}} + {{SubatomicParticle|link=yes|J/Psi}}}} (seen)

Double charmed omega†

| {{SubatomicParticle|Double charmed Omega+}}

| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Charm quark}}

|

| {{sfrac|1|2}}+

| +1

| −1

| +2

| 0

|

|

Charmed bottom omega†

| {{SubatomicParticle|Charmed bottom Omega0}}

| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Bottom quark}}

|

| {{sfrac|1|2}}+

| 0

| −1

| +1

| −1

|

|

Double bottom omega†

| {{SubatomicParticle|Double Bottom Omega-}}

| {{SubatomicParticle|link=yes|Strange quark}}{{SubatomicParticle|link=yes|Bottom quark}}{{SubatomicParticle|link=yes|Bottom quark}}

|

| {{sfrac|1|2}}+

| −1

| −1

| 0

| −2

|

|

Triple charmed omega†

| {{SubatomicParticle|Triple charmed Omega++}}

| {{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Charm quark}}

|

| {{sfrac|3|2}}+

| +2

| 0

| +3

| 0

|

|

Double charmed bottom omega†

| {{SubatomicParticle|Double charmed bottom Omega+}}

| {{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Bottom quark}}

|

| {{sfrac|1|2}}+

| +1

| 0

| +2

| −1

|

|

Charmed double bottom omega†

| {{SubatomicParticle|Charmed double bottom Omega0}}

| {{SubatomicParticle|link=yes|Charm quark}}{{SubatomicParticle|link=yes|Bottom quark}}{{SubatomicParticle|link=yes|Bottom quark}}

|

| {{sfrac|1|2}}+

| 0

| 0

| +1

| −2

|

|

Triple bottom omega†

| {{SubatomicParticle|Triple Bottom Omega-}}

| {{SubatomicParticle|link=yes|Bottom quark}}{{SubatomicParticle|link=yes|Bottom quark}}{{SubatomicParticle|link=yes|Bottom quark}}

|

| {{sfrac|3|2}}+

| −1

| 0

| 0

| −3

|

|

† Particle (or quantity, i.e. spin) has neither been observed nor indicated.

Recent discoveries

The {{SubatomicParticle|Bottom Omega-}} particle is a "doubly strange" baryon containing two strange quarks and a bottom quark. A discovery of this particle was first claimed in September 2008 by physicists working on the DØ experiment at the Tevatron facility of the Fermi National Accelerator Laboratory.

{{cite web

|date=3 September 2008

|title=Fermilab physicists discover "doubly strange" particle

|url=http://www.fnal.gov/pub/presspass/press_releases/Dzero_Omega-sub-b.html

|publisher=Fermilab

|access-date=2008-09-04

}}

{{cite journal

|author=V. Abazov et al. (DØ Collaboration)

|year=2008

|title=Observation of the doubly strange b baryon {{SubatomicParticle|Bottom Omega-}}

|journal=Physical Review Letters

|volume=101 |issue=23 |page=232002

|arxiv=0808.4142

|bibcode=2008PhRvL.101w2002A

|doi=10.1103/PhysRevLett.101.232002

|pmid=19113541

|s2cid=30481085

}} However, the reported mass of {{val|6165|16|ul=MeV/c2}} was significantly higher than expected in the quark model. The apparent discrepancy from the Standard Model has since been dubbed the "{{SubatomicParticle|Bottom Omega}} puzzle". In May 2009, the CDF collaboration made public their results on the search for the {{SubatomicParticle|Bottom Omega-}} based on analysis of a data sample roughly four times the size of the one used by the DØ experiment.

{{cite journal

|author=T. Aaltonen et al. (CDF Collaboration)

|year=2009

|title=Observation of the {{SubatomicParticle|Bottom Omega-}} and Measurement of the Properties of the {{SubatomicParticle|Bottom Xi-}} and {{SubatomicParticle|Bottom Omega-}}

|journal=Physical Review D

|volume=80 |issue=7 |pages=072003

|arxiv=0905.3123

|bibcode=2009PhRvD..80g2003A

|doi=10.1103/PhysRevD.80.072003

|hdl=1721.1/52706

|s2cid=54189461

}} CDF measured the mass to be {{val|6054.4|6.8|u=MeV/c2}}, which was in excellent agreement with the Standard Model prediction. No signal has been observed at the DØ reported value. The two results differ by {{val|111|18|u=MeV/c2}}, which is equivalent to 6.2 standard deviations and are therefore inconsistent. Excellent agreement between the CDF measured mass and theoretical expectations is a strong indication that the particle discovered by CDF is indeed the {{SubatomicParticle|Bottom Omega-}}. In February 2013 the LHCb collaboration published a measurement of the {{SubatomicParticle|Bottom Omega-}} mass that is consistent with, but more precise than, the CDF result.{{cite journal

|author=R. Aaij et al. (LHCb collaboration)

|year=2013

|title=Measurement of the {{SubatomicParticle|Bottom Lambda0}}, {{SubatomicParticle|Bottom Xi-}} and {{SubatomicParticle|Bottom Omega-}} baryon masses

|journal=Physical Review Letters

|volume=110 |issue=18 |page=182001

|arxiv=1302.1072

|bibcode=2013PhRvL.110r2001A

|doi=10.1103/PhysRevLett.110.182001

|pmid=23683191

|s2cid=22966047

}}

In March 2017, the LHCb collaboration announced the observation of five new narrow {{SubatomicParticle|Charmed Omega0}} states decaying to {{SubatomicParticle|Charmed Xi+}}{{SubatomicParticle|Kaon-}}, where the {{SubatomicParticle|Charmed Xi+}} was reconstructed in the decay mode {{SubatomicParticle|proton}}{{SubatomicParticle|Kaon-}}{{SubatomicParticle|pion+}}.{{cite web|title=LHCb observes an exceptionally large group of particles|publisher=CERN|url=http://home.cern/about/updates/2017/03/lhcb-observes-exceptionally-large-group-particles}}{{cite journal|author=R. Aaij et al. (LHCb collaboration)|title=Observation of five new narrow {{SubatomicParticle|Charmed Omega0}} states decaying to {{SubatomicParticle|Charmed Xi+}}{{SubatomicParticle|Kaon-}}|year=2017|journal=Physical Review Letters|volume=11801|issue=2017|pages=182001|arxiv=1703.04639|bibcode=2017PhRvL.118r2001A|doi=10.1103/PhysRevLett.118.182001|pmid=28524669|s2cid=610517}} The states are named {{SubatomicParticle|Charmed Omega}}(3000)0, {{SubatomicParticle|Charmed Omega}}(3050)0, {{SubatomicParticle|Charmed Omega}}(3066)0, {{SubatomicParticle|Charmed Omega}}(3090)0 and {{SubatomicParticle|Charmed Omega}}(3119)0. Their masses and widths were reported, but their quantum numbers could not be determined due to the large background present in the sample.

See also

References

{{Reflist|30em}}

External links

  • [https://www.flickr.com/photos/brookhavenlab/3148786892/in/album-72157611796003039/ Picture of the first event containing the {{SubatomicParticle|Omega-}}, which happens to contain the complete decay chain of the {{SubatomicParticle|Omega-}}].
  • [https://www.sciencedaily.com/releases/2008/09/080903172201.htm Science Daily – Discovery of the {{SubatomicParticle|Bottom Omega-}}]
  • [http://www.bbc.co.uk/programmes/p01z4p1j Strangeness Minus Three - BBC Horizon 1964]

{{Particles}}

Category:Baryons

Category:Murray Gell-Mann