Omega particle
Encyclopedia
The Omega baryons are a family of subatomic
hadron
particles which have the symbols
and have a +2, +1 or -1 elementary charge
or are neutral
. They are baryon
s containing no up
or down
quark
s. Omega Baryons containing top quark
s are not expected to be observed as the Standard Model
predicts the mean lifetime of top quarks to be roughly . This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons
.
The first Omega baryon discovered was the , made of three strange quark
s, in 1964. 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 by American
physicist
Murray Gell-Mann
in 1962 and independently by Yuval Ne'eman
. Besides the , a charmed Omega particle was discovered, 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
(J) and parity
(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.
† Particle (or quantity, i.e. spin) has neither been observed nor indicated.
" 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 DZero experiment at the Fermi National Accelerator Laboratory. However, the reported mass, , was significantly higher than expected in quark model
. The apparent discrepancy from Standard Model
has since been dubbed " puzzle". In May 2009 the CDF
collaboration made public their results on search for based on analysis of data sample roughly four times larger than the one used by DØ experiment. CDF
measured mass to be in excellent agreement with Standard Model prediction. No signal has been observed at DZero reported value. The two results differ by or by 6.2 standard deviations and therefore are inconsistent. Excellent agreement between CDF measured mass and theoretical expectations is a strong indication that the particle discovered by CDF is indeed the .
Subatomic particle
In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...
hadron
Hadron
In particle physics, a hadron is a composite particle made of quarks held together by the strong force...
particles which have the symbols
and have a +2, +1 or -1 elementary charge
Elementary charge
The elementary charge, usually denoted as e, is the electric charge carried by a single proton, or equivalently, the absolute value of the electric charge carried by a single electron. This elementary charge is a fundamental physical constant. To avoid confusion over its sign, e is sometimes called...
or are neutral
Neutral particle
In physics, a neutral particle is a particle with no electric charge. This is not to be confused with a real neutral particle, a neutral particle that is also identical to its own antiparticle.-Stable or long-lived neutral particles:...
. They are baryon
Baryon
A baryon is a composite particle made up of three quarks . Baryons and mesons belong to the hadron family, which are the quark-based particles...
s containing no up
Up quark
The up quark or u quark is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons and protons of atomic nuclei...
or down
Down quark
The down quark or d quark is the second-lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the up quark, forms the neutrons and protons of atomic nuclei...
quark
Quark
A quark is an 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. Due to a phenomenon known as color confinement, quarks are never directly...
s. Omega Baryons containing top quark
Top quark
The top quark, also known as the t quark or truth quark, is an elementary particle and a fundamental constituent of matter. Like all quarks, the top quark is an elementary fermion with spin-, and experiences all four fundamental interactions: gravitation, electromagnetism, weak interactions, and...
s are not expected to be observed as the Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...
predicts the mean lifetime of top quarks to be roughly . This is about 20 times shorter than the timescale for strong interactions, and therefore it does not form hadrons
Hadronization
In particle physics, hadronization is the process of the formation of hadrons out of quarks and gluons. This occurs after high-energy collisions in a particle collider in which free quarks or gluons are created. Due to postulated colour confinement, these cannot exist individually...
.
The first Omega baryon discovered was the , made of three strange quark
Strange quark
The strange quark or s quark is the third-lightest of all quarks, a type of elementary particle. Strange quarks are found in hadrons, which are subatomic particles. Example of hadrons containing strange quarks include kaons , strange D mesons , Sigma baryons , and other strange particles...
s, in 1964. The discovery was a great triumph in the study of quark
Quark
A quark is an 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. Due to a phenomenon known as color confinement, quarks are never directly...
processes, since it was found only after its existence, mass, and decay products had been predicted by American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
Murray Gell-Mann
Murray Gell-Mann
Murray Gell-Mann is an American physicist and linguist who received the 1969 Nobel Prize in physics for his work on the theory of elementary particles...
in 1962 and independently by Yuval Ne'eman
Yuval Ne'eman
Yuval Ne'eman , was a renowned Israeli theoretical physicist, military scientist, and politician. He was a minister in the Israeli government in the 1980s and early 1990s.-Biography:...
. Besides the , a charmed Omega particle was discovered, in which a strange quark is replaced by a charm quark
Charm quark
The charm quark or c quark is the third most massive of all quarks, a type of elementary particle. Charm quarks are found in hadrons, which are subatomic particles made of quarks...
. The decays only via the weak interaction and has therefore a relatively long lifetime. Spin
Spin (physics)
In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,...
(J) and parity
Parity (physics)
In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:...
(P) values for unobserved baryons are predicted by the quark model
Quark model
In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons....
.
Since Omega baryons do not have any up or down quarks, they all have isospin
Isospin
In physics, and specifically, particle physics, isospin is a quantum number related to the strong interaction. This term was derived from isotopic spin, but the term is confusing as two isotopes of a nucleus have different numbers of nucleons; in contrast, rotations of isospin maintain the number...
0.
Omega baryons
| Particle | Symbol | Quark content |
Rest mass MeV/c Speed of light The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time... 2 |
J Spin (physics) In quantum mechanics and particle physics, spin is a fundamental characteristic property of elementary particles, composite particles , and atomic nuclei.It is worth noting that the intrinsic property of subatomic particles called spin and discussed in this article, is related in some small ways,... P Parity (physics) In physics, a parity transformation is the flip in the sign of one spatial coordinate. In three dimensions, it is also commonly described by the simultaneous flip in the sign of all three spatial coordinates:... |
Q Charge (physics) In physics, a charge may refer to one of many different quantities, such as the electric charge in electromagnetism or the color charge in quantum chromodynamics. Charges are associated with conserved quantum numbers.-Formal definition:... |
S Strangeness In particle physics, strangeness S is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic reactions, which occur in a short period of time... |
C | B Bottomness In physics, bottomness also called beauty, is a flavour quantum number reflecting the difference between the number of bottom antiquarks and the number of bottom quarks that are present in a particle: B^\prime = -Bottom quarks have a bottomness of −1 while bottom antiquarks have a... |
Mean lifetime s Second The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock.... |
Decays to |
|---|---|---|---|---|---|---|---|---|---|---|
| Omega | 1672.45±0.29 | + | −1 | −3 | 0 | 0 | or or |
|||
| Charmed Omega | 2697.5±2.6 | + | 0 | −2 | +1 | 0 | See Decay Modes | |||
| Bottom Omega | 6054.4±6.8 | + | −1 | −2 | 0 | −1 | (seen) | |||
| Double charmed Omega† | + | +1 | −1 | +2 | 0 | |||||
| Charmed bottom Omega† | + | 0 | −1 | −1 | −1 | |||||
| Double bottom Omega† | + | −1 | −1 | 0 | −2 | |||||
| Triple charmed Omega† | + | +2 | 0 | +3 | 0 | |||||
| Double charmed bottom Omega† | + | +1 | 0 | +2 | −1 | |||||
| Charmed double bottom Omega† | + | 0 | 0 | +1 | −2 | |||||
| Triple bottom Omega† | + | −1 | 0 | 0 | −3 | |||||
† Particle (or quantity, i.e. spin) has neither been observed nor indicated.
Recent discoveries
The particle is a "doubly strangeStrangeness
In particle physics, strangeness S is a property of particles, expressed as a quantum number, for describing decay of particles in strong and electromagnetic reactions, which occur in a short period of time...
" baryon
Baryon
A baryon is a composite particle made up of three quarks . Baryons and mesons belong to the hadron family, which are the quark-based particles...
containing two strange quarks and a bottom quark
Bottom quark
The bottom quark, also known as the beauty quark, is a third-generation quark with a charge of − e. Although all quarks are described in a similar way by the quantum chromodynamics, the bottom quark's large bare mass , combined with low values of the CKM matrix elements Vub and Vcb, gives it a...
. A discovery of this particle was first claimed in September 2008 by physicists working on the DZero experiment at the Fermi National Accelerator Laboratory. However, the reported mass, , was significantly higher than expected in quark model
Quark model
In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks—the quarks and antiquarks which give rise to the quantum numbers of the hadrons....
. The apparent discrepancy from Standard Model
Standard Model
The Standard Model of particle physics is a theory concerning the electromagnetic, weak, and strong nuclear interactions, which mediate the dynamics of the known subatomic particles. Developed throughout the mid to late 20th century, the current formulation was finalized in the mid 1970s upon...
has since been dubbed " puzzle". In May 2009 the CDF
Collider Detector at Fermilab
The Collider Detector at Fermilab experimental collaboration studies high energy particle collisions at the Tevatron,the world's former highest-energy particle accelerator...
collaboration made public their results on search for based on analysis of data sample roughly four times larger than the one used by DØ experiment. CDF
Collider Detector at Fermilab
The Collider Detector at Fermilab experimental collaboration studies high energy particle collisions at the Tevatron,the world's former highest-energy particle accelerator...
measured mass to be in excellent agreement with Standard Model prediction. No signal has been observed at DZero reported value. The two results differ by or by 6.2 standard deviations and therefore are inconsistent. Excellent agreement between CDF measured mass and theoretical expectations is a strong indication that the particle discovered by CDF is indeed the .
See also
- Delta baryonDelta baryonThe Delta baryons are a family of subatomic hadron particles which have the symbols , , , and and electric charges +2, +1, 0 and -1 elementary charge respectively...
- HyperonHyperonIn particle physics, a hyperon is any baryon containing one or more strange quarks, but no charm quarks or bottom quarks.-Properties and behavior of hyperons:...
- Lambda baryon
- List of mesons
- List of particles
- NucleonNucleonIn physics, a nucleon is a collective name for two particles: the neutron and the proton. These are the two constituents of the atomic nucleus. Until the 1960s, the nucleons were thought to be elementary particles...
- Physics portal
- Sigma baryonSigma baryonThe Sigma baryons are a family of subatomic hadron particles which have a +2, +1 or -1 elementary charge or are neutral. They are baryons containing three quarks: two up and/or down quarks, and one third quark, which can be either a strange , a charm , a bottom or a top quark...
- Timeline of particle discoveriesTimeline of particle discoveriesThis is a timeline of subatomic particle discoveries, including all particles thus far discovered which appear to be elementary given the best available evidence...
- Xi baryon