The omega baryons are a family of subatomic hadron (a baryon) particles that are represented by the symbol and are either neutral or have a +2, +1 or −1

elementary charge The elementary charge, usually denoted by is the electric charge carried by a single proton or, equivalently, the magnitude of the negative electric charge carried by a single electron, which has charge −1 . This elementary charge is a fundame ...

. They are baryons containing no up or

down Down most often refers to: * Down, the relative direction opposed to up * Down (gridiron football), in American/Canadian football, a period when one play takes place * Down feather, a soft bird feather used in bedding and clothing * Downland, a ty ...

quark A quark () is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. All commonly o ...

s. Omega baryons containing top quarks are not expected to be observed. This is because the

Standard Model The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetism, electromagnetic, weak interaction, weak and strong interactions - excluding gravity) in the universe and classifying a ...

predicts the mean lifetime of top quarks to be roughly , which is about a twentieth of the timescale for

strong interaction The strong interaction or strong force is a fundamental interaction that confines quarks into proton, neutron, and other hadron particles. The strong interaction also binds neutrons and protons to create atomic nuclei, where it is called the n ...

s, and therefore that they do not form hadrons. The first omega baryon discovered was the , made of three

strange quark 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 ( ...

s, in 1964. The discovery was a great triumph in the study of

processes, since it was found only after its existence, mass, and decay products had been predicted in 1961 by the

American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

physicist Murray Gell-Mann and, independently, by the Israeli physicist Yuval Ne'eman. Besides the , a charmed omega particle () was discovered in 1985, in which a strange quark is replaced by a charm quark. The decays only via the weak interaction and has therefore a relatively long lifetime.

Spin Spin or spinning most often refers to: * Spinning (textiles), the creation of yarn or thread by twisting fibers together, traditionally by hand spinning * Spin, the rotation of an object around a central axis * Spin (propaganda), an intentionally b ...

(''J'') and

parity Parity may refer to: * Parity (computing) ** Parity bit in computing, sets the parity of data for the purpose of error detection ** Parity flag in computing, indicates if the number of set bits is odd or even in the binary representation of the r ...

(''P'') values for unobserved baryons are predicted by the quark model. Since omega baryons do not have any up or down quarks, they all have isospin 0.

Omega baryons

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

Recent discoveries

The particle is a "doubly

strange Strange may refer to: Fiction * Strange (comic book), a comic book limited series by Marvel Comics * Strange (Marvel Comics), one of a pair of Marvel Comics characters known as The Strangers * Adam Strange, a DC Comics superhero * The title char ...

" 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. However, the reported mass of was significantly higher than expected in the quark model. The apparent discrepancy from the

has since been dubbed the " puzzle". In May 2009, the CDF collaboration made public their results on the search for the based on analysis of a data sample roughly four times the size of the one used by the

DØ experiment The DØ experiment (sometimes written D0 experiment, or DZero experiment) was a worldwide collaboration of scientists conducting research on the fundamental nature of matter. DØ was one of two major experiments (the other was the CDF experim ...

. CDF measured the mass to be , 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 , 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 . In February 2013 the LHCb collaboration published a measurement of the mass that is consistent with, but more precise than, the CDF result. In March 2017, the LHCb collaboration announced the observation of five new narrow states decaying to , where the was reconstructed in the decay mode . The states are named (3000)⁰, (3050)⁰, (3066)⁰, (3090)⁰ and (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.

References

External links

Picture of the first event containing the , which happens to contain the complete decay chain of the

Strangeness Minus Three - BBC Horizon 1964
{{Particles Baryons

Omega baryons

Recent discoveries

See also

References

External links