Eta meson
Encyclopedia
}}}
| statistics = Bosonic
| group = Meson
s
| generation =
| interaction = Strong
, Weak
| antiparticle = Self
| theorized =
| discovered =
| symbol = ,
| mass =
| decay_particle = :
or
:
| electric_charge =
| color_charge =
| spin = Integer
| num_spin_states =
}}
The eta and eta prime meson are meson
s made of a mixture of up
, down
and strange
quark
s and their antiquarks. The charmed eta meson and bottom eta meson are forms of quarkonium
; they have the same spin
and parity
as the light eta but are made of charm quark
s and bottom quark
s respectively. The top quark
is too heavy to form a similar meson (top eta meson, symbol ), due to its very fast decay.
The eta was discovered in pion
-nucleon
collisions at the Bevatron
in 1961.
The difference between the mass of the η and that of the η' is larger than the quark model
can naturally explain. This "η-η' puzzle" is resolved by instanton
s.
| statistics = Bosonic
| group = Meson
Meson
In particle physics, mesons are subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometer: 10−15 m, which is about the size of a proton...
s
| generation =
| interaction = Strong
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...
, Weak
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...
| antiparticle = Self
| theorized =
| discovered =
| symbol = ,
| mass =
| decay_particle = :
or
:
| electric_charge =
| color_charge =
| spin = Integer
Boson
In particle physics, bosons are subatomic particles that obey Bose–Einstein statistics. Several bosons can occupy the same quantum state. The word boson derives from the name of Satyendra Nath Bose....
| num_spin_states =
}}
The eta and eta prime meson are meson
Meson
In particle physics, mesons are subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometer: 10−15 m, which is about the size of a proton...
s made of a mixture of 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...
, 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...
and strange
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...
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 and their antiquarks. The charmed eta meson and bottom eta meson are forms of quarkonium
Quarkonium
In particle physics, quarkonium designates a flavorless meson whose constituents are a quark and its own antiquark. Examples of quarkonia are the J/ψ meson and the meson...
; they have the same 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 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:...
as the light eta but are made of 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 and 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 respectively. The 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...
is too heavy to form a similar meson (top eta meson, symbol ), due to its very fast decay.
The eta was discovered in pion
Pion
In particle physics, a pion is any of three subatomic particles: , , and . Pions are the lightest mesons and they play an important role in explaining the low-energy properties of the strong nuclear force....
-nucleon
Nucleon
In 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...
collisions at the Bevatron
Bevatron
The Bevatron was a historic particle accelerator — specifically, a weak-focusing proton synchrotron — at Lawrence Berkeley National Laboratory, U.S.A., which began operating in 1954. The antiproton was discovered there in 1955, resulting in the 1959 Nobel Prize in physics for Emilio...
in 1961.
The difference between the mass of the η and that of the η' is larger than 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....
can naturally explain. This "η-η' puzzle" is resolved by instanton
Instanton
An instanton is a notion appearing in theoretical and mathematical physics. Mathematically, a Yang–Mills instanton is a self-dual or anti-self-dual connection in a principal bundle over a four-dimensional Riemannian manifold that plays the role of physical space-time in non-abelian gauge theory...
s.
External links
- Eta Meson at the Particle Data Group