ART

The omega baryons are a family of subatomic hadron (a baryon) particles that are represented by the symbol Ω and are either neutral or have a +2, +1 or −1 elementary charge. They are baryons containing no up or down quarks.[1] Omega baryons containing top quarks are not expected to be observed. This is because the Standard Model predicts the mean lifetime of top quarks to be roughly 5×10−25 s ,[2] which is about a twentieth of the timescale for strong interactions, and therefore that they do not form hadrons.

The first omega baryon discovered was the \( \Omega ^{-} \) , made of three strange quarks, in 1964.[3] The discovery was a great triumph in the study of quark processes, 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 \( \Omega ^{-} \) , a charmed omega particle (\( \Omega _{c}^{0} \)) was discovered, in which a strange quark is replaced by a charm quark. The \( \Omega ^{-} \) decays only via the weak interaction and has therefore a relatively long lifetime.[4] Spin (J) and parity (P) values for unobserved baryons are predicted by the quark model.[5]

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

Omega baryons

Omega
Particle Symbol Quark
content
Rest mass
(MeV/c2)
JP Q
(e)
S C B′ Mean lifetime
(s)
Decays to
Omega[6] \( \Omega ^{-} \)
sss
1672.45±0.29 3/2+ −1 −3 0 0 (8.21±0.11)×10−11
Λ0+ K
or

Ξ0+ π
or

Ξ+ π0

Charmed omega[7] \( \Omega _{c}^{0} \)
ssc
2697.5±2.6 1/2+ 0 −2 +1 0 (6.9±1.2)×10−14 See
Ω0c Decay Modes
Bottom omega[8] \( \Omega _{b}^{-} \)
ssb
6054.4±6.8 1/2+ −1 −2 0 −1 (1.13±0.53)×10−12
Ω+ J/ψ
(seen)
Double charmed omega† \( \Omega _{cc}^{+} \)
scc
1/2+ +1 −1 +2 0
Charmed bottom omega† \( \Omega _{cb}^{0} \)
scb
1/2+ 0 −1 +1 −1
Double bottom omega† \( \Omega _{bb}^{-} \)
sbb
1/2+ −1 −1 0 −2
Triple charmed omega† \( \Omega _{ccc}^{++} \)
ccc
3/2+ +2 0 +3 0
Double charmed bottom omega† \( \Omega _{ccb}^{+} \)
ccb
1/2+ +1 0 +2 −1
Charmed double bottom omega† \(\Omega _{cbb}^{0} \)
cbb
1/2+ 0 0 +1 −2
Triple bottom omega† \( \Omega _{bbb}^{-} \)
bbb
3/2+ −1 0 0 −3

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

The \( \Omega _{b}^{-} \) 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.[9][10] However, the reported mass of 6165±16 MeV/c2 was significantly higher than expected in the quark model. The apparent discrepancy from the Standard Model has since been dubbed the " Ω b puzzle". In May 2009, the CDF collaboration made public their results on the search for the \( \Omega _{b}^{-} \) based on analysis of a data sample roughly four times the size of the one used by the DØ experiment.[8] CDF measured the mass to be 6054.4±6.8 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 111±18 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 \( \Omega _{b}^{-} \) . In February 2013 the LHCb collaboration published a measurement of the \( \Omega _{b}^{-} \) mass that is consistent with, but more precise than, the CDF result.[11]

In March 2017, the LHCb collaboration announced the observation of five new narrow \( \Omega _{c}^{0} \) states decaying to Ξ+cK−, where the Ξ+ c was reconstructed in the decay mode pK−π+.[12][13] The states are named Ωc(3000)0, Ωc(3050)0, Ωc(3066)0, Ωc(3090)0 and Ωc(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

Delta baryon
Hyperon
Lambda baryon
List of mesons
List of particles
Nucleon
Physics portal
Sigma baryon
Timeline of particle discoveries
Xi baryon

References

Particle Data Group. "2010 Review of Particle Physics – Naming scheme for hadrons" (PDF). Retrieved 26 December 2011.
A. Quadt (2006). "Top quark physics at hadron colliders". European Physical Journal C. 48 (3): 835–1000. Bibcode:2006EPJC...48..835Q. doi:10.1140/epjc/s2006-02631-6.
V. E. Barnes; et al. (1964). "Observation of a Hyperon with Strangeness Minus Three" (PDF). Physical Review Letters. 12 (8): 204. Bibcode:1964PhRvL..12..204B. doi:10.1103/PhysRevLett.12.204.
R. Nave. "The Omega baryon". HyperPhysics. Retrieved 26 November 2009.
Körner, J.G; Krämer, M; Pirjol, D (1 January 1994). "Heavy baryons". Progress in Particle and Nuclear Physics. 33: 787–868.arXiv:hep-ph/9406359. Bibcode:1994PrPNP..33..787K. doi:10.1016/0146-6410(94)90053-1.
Particle Data Group. "2006 Review of Particle Physics – Ω−" (PDF). Retrieved 20 April 2008.
Particle Data Group. "
Ω0 c listing –
Ω0 c" (PDF). Retrieved 13 August 2018.
T. Aaltonen et al. (CDF Collaboration) (2009). "Observation of the
Ω−b and Measurement of the Properties of the
Ξ−b andΩ−b". Physical Review D. 80 (7): 072003.arXiv:0905.3123. Bibcode:2009PhRvD..80g2003A. doi:10.1103/PhysRevD.80.072003. hdl:1721.1/52706.
"Fermilab physicists discover "doubly strange" particle". Fermilab. 3 September 2008. Retrieved 4 September 2008.
V. Abazov et al. (DØ Collaboration) (2008). "Observation of the doubly strange b baryon
Ω−b". Physical Review Letters. 101 (23): 232002.arXiv:0808.4142. Bibcode:2008PhRvL.101w2002A. doi:10.1103/PhysRevLett.101.232002. PMID 19113541.
R. Aaij et al. (LHCb collaboration) (2013). "Measurement of the
Λ0 b,Ξ−b andΩ−b baryon masses". Physical Review Letters. 110 (18): 182001.arXiv:1302.1072. Bibcode:2013PhRvL.110r2001A. doi:10.1103/PhysRevLett.110.182001. PMID 23683191.
"LHCb observes an exceptionally large group of particles". CERN.

R. Aaij et al. (LHCb collaboration) (2017). "Observation of five new narrow Ω0 c states decaying to Ξ+ c K−
". Physical Review Letters. 11801 (2017): 182001.arXiv:1703.04639. Bibcode:2017PhRvL.118r2001A. doi:10.1103/PhysRevLett.118.182001. PMID 28524669.

External links

Picture of the first event containing the Ω− , which happens to contain the complete decay chain of the Ω− .
Science Daily – Discovery of the Ω− b
Strangeness Minus Three - BBC Horizon 1964

vte

Particles in physics
Elementary
Fermions
Quarks

Up (quark antiquark) Down (quark antiquark) Charm (quark antiquark) Strange (quark antiquark) Top (quark antiquark) Bottom (quark antiquark)

Leptons

Electron Positron Muon Antimuon Tau Antitau Electron neutrino Electron antineutrino Muon neutrino Muon antineutrino Tau neutrino Tau antineutrino

Bosons
Gauge

Photon Gluon W and Z bosons

Scalar

Higgs boson

Ghost fields

Faddeev–Popov ghosts

Hypothetical
Superpartners
Gauginos

Gluino Gravitino Photino

Others

Axino Chargino Higgsino Neutralino Sfermion (Stop squark)

Others

Axion Curvaton Dilaton Dual graviton Graviphoton Graviton Inflaton Leptoquark Magnetic monopole Majoron Majorana fermion Dark photon Planck particle Preon Sterile neutrino Tachyon W′ and Z′ bosons X and Y bosons

Composite
Hadrons
Baryons

Nucleon
Proton Antiproton Neutron Antineutron Delta baryon Lambda baryon Sigma baryon Xi baryon Omega baryon

Mesons

Pion Rho meson Eta and eta prime mesons Phi meson J/psi meson Omega meson Upsilon meson Kaon B meson D meson Quarkonium

Exotic hadrons

Tetraquark Pentaquark

Others

Atomic nuclei Atoms Exotic atoms
Positronium Muonium Tauonium Onia Pionium Superatoms Molecules

Hypothetical
Baryons

Hexaquark Heptaquark Skyrmion

Mesons

Glueball Theta meson T meson

Others

Mesonic molecule Pomeron Diquark R-hadron

Quasiparticles

Anyon Davydov soliton Dropleton Exciton Hole Magnon Phonon Plasmaron Plasmon Polariton Polaron Roton Trion

Lists

Baryons Mesons Particles Quasiparticles Timeline of particle discoveries

Related

History of subatomic physics
timeline Standard Model
mathematical formulation Subatomic particles Particles Antiparticles Nuclear physics Eightfold way
Quark model Exotic matter Massless particle Relativistic particle Virtual particle Wave–particle duality Particle chauvinism

Wikipedia books

Hadronic Matter Particles of the Standard Model Leptons Quarks

Physics Encyclopedia

World

Index

Hellenica World - Scientific Library

Retrieved from "http://en.wikipedia.org/"
All text is available under the terms of the GNU Free Documentation License