Hyperon
Encyclopedia
In particle physics
, a hyperon is any baryon
containing one or more strange quark
s, but no charm quark
s or bottom quark
s.
Being baryons, all hyperons are fermion
s. That is, they have half-integer
spin
and obey Fermi-Dirac statistics
. They 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. Hyperons decay weakly
with non-conserved parity
.
There is one Lambda hyperon, . It has a rest energy of with a lifetime of .
There are two Xi hyperons, and . They have rest energies of and and lifetimes of and .
There is one Omega hyperon, the last discovered, , with a mass of and a lifetime of .
is conserved by the strong interaction
s, the ground-state hyperons cannot decay strongly. However, they do participate in strong interactions.
may also decay on rare occurrences via these processes:
particles are also known as "cascade" hyperons, since they go through a two-step cascading decay into a nucleon by first decaying to a and emitting a .
of −2, giving it strangeness of −3.
It takes multiple flavor-changing weak decays
for it to decay into a proton or neutron. Murray Gell-Mann
's SU(3)
model (sometimes called the 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.
, Fermilab
, SLAC, JLAB
, Brookhaven National Laboratory
, KEK
, and others. Physics topics include searches for CP violation
, measurements of spin
, studies of excited state
s (commonly referred to as spectroscopy), and hunts for exotic states such as pentaquark
s and dibaryon
s.
Particle physics
Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...
, a hyperon is any 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 one or more 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, but no 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...
s or 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...
s.
Properties and behavior of hyperons
Fermion
In particle physics, a fermion is any particle which obeys the Fermi–Dirac statistics . Fermions contrast with bosons which obey Bose–Einstein statistics....
s. That is, they have half-integer
Half-integer
In mathematics, a half-integer is a number of the formn + 1/2,where n is an integer. For example,are all half-integers. Note that a half of an integer is not always a half-integer: half of an even integer is an integer but not a half-integer...
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,...
and obey Fermi-Dirac statistics
Fermi-Dirac statistics
Fermi–Dirac statistics is a part of the science of physics that describes the energies of single particles in a system comprising many identical particles that obey the Pauli Exclusion Principle...
. They all interact via the strong nuclear force, making them types of hadron
Hadron
In particle physics, a hadron is a composite particle made of quarks held together by the strong force...
. They are composed of three light 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, at least one of which is a 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...
, which makes them strange baryons. Hyperons decay weakly
Weak interaction
Weak interaction , is one of the four fundamental forces of nature, alongside the strong nuclear force, electromagnetism, and gravity. It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars...
with non-conserved 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:...
.
Types of hyperons
There are three Sigma hyperons, , and . They have rest energies of ~ and lifetimes of ~ with the exception of whose lifetime is shorter than .There is one Lambda hyperon, . It has a rest energy of with a lifetime of .
There are two Xi hyperons, and . They have rest energies of and and lifetimes of and .
There is one Omega hyperon, the last discovered, , with a mass of and a lifetime of .
Hyperon decay
Since strangenessStrangeness
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...
is conserved by the strong interaction
Strong interaction
In particle physics, the strong interaction is one of the four fundamental interactions of nature, the others being electromagnetism, the weak interaction and gravitation. As with the other fundamental interactions, it is a non-contact force...
s, the ground-state hyperons cannot decay strongly. However, they do participate in strong interactions.
Λ decay
- → +
- → +
may also decay on rare occurrences via these processes:
- → + +
- → + +
Σ decay
- → +
- → +
- → +
- → +
Ξ decay
- → +
- → +
particles are also known as "cascade" hyperons, since they go through a two-step cascading decay into a nucleon by first decaying to a and emitting a .
Ω− decay
The has a baryon number of +1 and hyperchargeHypercharge
In particle physics, the hypercharge Y of a particle is related to the strong interaction, and is distinct from the similarly named weak hypercharge, which has an analogous role in the electroweak interaction...
of −2, giving it strangeness of −3.
It takes multiple flavor-changing weak decays
Weak interaction
Weak interaction , is one of the four fundamental forces of nature, alongside the strong nuclear force, electromagnetism, and gravity. It is responsible for the radioactive decay of subatomic particles and initiates the process known as hydrogen fusion in stars...
for it to decay into a proton or neutron. 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...
's SU(3)
Special unitary group
The special unitary group of degree n, denoted SU, is the group of n×n unitary matrices with determinant 1. The group operation is that of matrix multiplication...
model (sometimes called the Eightfold Way
Eightfold way (physics)
In physics, the Eightfold Way is a term coined by American physicist Murray Gell-Mann for a theory organizing subatomic baryons and mesons into octets...
) 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
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...
. Further examples of its formation and observation using particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
s confirmed the SU(3) model.
- → +
- → +
- → +
Hyperon research
The first research into hyperons happened in the 1950s, and spurred physicists on to the creation of an organized classification of particles. Today, research in this area is carried out on data taken at many facilities around the world, including CERNCERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
, Fermilab
Fermilab
Fermi National Accelerator Laboratory , located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics...
, SLAC, JLAB
JLab
jLab is a numerical computational environment implemented in Java. The main scripting engine of jLab is GroovySci, an extension of Groovy. Additionally, the interpreted J-Scripts and dynamic linking to Java class code are supported....
, Brookhaven National Laboratory
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...
, KEK
KEK
, known as KEK, is a national organization whose purpose is to operate the largest particle physics laboratory in Japan, which is situated in Tsukuba of Ibaraki prefecture. Established in 1997. The term "KEK" is also used to refer to the laboratory itself, which employs approximately 900 employees...
, and others. Physics topics include searches for CP violation
CP violation
In particle physics, CP violation is a violation of the postulated CP-symmetry: the combination of C-symmetry and P-symmetry . CP-symmetry states that the laws of physics should be the same if a particle were interchanged with its antiparticle , and left and right were swapped...
, measurements of 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,...
, studies of excited state
Excited state
Excitation is an elevation in energy level above an arbitrary baseline energy state. In physics there is a specific technical definition for energy level which is often associated with an atom being excited to an excited state....
s (commonly referred to as spectroscopy), and hunts for exotic states such as pentaquark
Pentaquark
A pentaquark is a hypothetical subatomic particle consisting of four quarks and one antiquark bound together . As quarks have a baryon number of +, and antiquarks of −, it would have a total baryon number of 1, thus being classified as an exotic baryon...
s and dibaryon
Dibaryon
Dibaryons are a large family of hypothetical particles that would consist of six quarks of any flavours. They are predicted to be fairly stable once formed...
s.
List of hyperons
| Particle | Symbol | Makeup | 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 |
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... I 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... |
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,... (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:... ) 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.... |
Commonly decays to |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Lambda | 1 115.683(6) | 0 | + | 0 | −1 | 0 | 0 | or |
|||
| Sigma Sigma baryon The 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... |
1 189.37(0.7) | 1 | + | +1 | −1 | 0 | 0 | or |
|||
| Sigma Sigma baryon The 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... |
1 192.642(24) | 1 | + | 0 | −1 | 0 | 0 | ||||
| Sigma Sigma baryon The 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... |
1 197.449(30) | 1 | + | −1 | −1 | 0 | 0 | ||||
| Sigma Sigma baryon The 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... resonance |
(1385) | 1 382.8(4) | 1 | + | +1 | −1 | 0 | 0 | or | ||
| Sigma Sigma baryon The 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... resonance |
(1385) | 1 383.7±1.0 | 1 | + | 0 | −1 | 0 | 0 | or | ||
| Sigma Sigma baryon The 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... resonance |
(1385) | 1 387.2(5) | 1 | + | −1 | −1 | 0 | 0 | or | ||
| Xi | 1 314.83(20) | + | 0 | −2 | 0 | 0 | |||||
| Xi | 1 321.31(13) | + | −1 | −2 | 0 | 0 | |||||
| Xi resonance | (1530) | 1 531.80(32) | + | 0 | −2 | 0 | 0 | ||||
| Xi resonance | (1530) | 1 535.0(6) | + | −1 | −2 | 0 | 0 | ||||
| Omega | 1 672.45(29) | 0 | + | −1 | −3 | 0 | 0 | or or |
|||
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...
- HypernucleusHypernucleusA hypernucleus is a nucleus which contains at least one hyperon in addition to nucleons. The first was discovered by Marian Danysz and Jerzy Pniewski in 1952....
- 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...
- Omega baryon
- 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