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Strong interaction
 
 
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In particle physics, the strong interaction, or strong force, or color force, holds quark
Quark

Quarks are a type of elementary particle and major constituents of matter. They are the only particles in the Standard Model to experience all four fundamental interaction, which are also known as fundamental interactions....
s and gluon
Gluon

Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei....
s together to form proton
Proton

The proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H+....
s, neutron
Neutron

The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutrons are usually found in atomic nucleus....
s and other particles. The strong interaction is one of the four fundamental interaction
Fundamental interaction

In physics, a fundamental interaction or fundamental force is a process by which elementary particles interact with each other. An interaction is often described as a field , and is mediated by the exchange of gauge bosons between particles....
s, along with gravitation
Gravitation

Gravitation is a natural phenomenon that gives weight to objects. In everyday life, attraction due to gravity is the result of the presence of relatively large bodies, such as the Earth and the Moon....
, the electromagnetic force
Electromagnetic force

In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. It is the electromagnetic force that holds electrons and protons together in atoms, and which hold atoms together to make molecules....
 and the weak interaction
Weak interaction

The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
. The word strong is used since the strong interaction is the most powerful of the four fundamental forces; its typical field strength is 100 times the strength of the electromagnetic force
Electromagnetic force

In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. It is the electromagnetic force that holds electrons and protons together in atoms, and which hold atoms together to make molecules....
, some 1013 times as great as that of the weak force, and about 1038 times that of gravitation.

The strong force is thought to be mediated by gluons, acting upon quark
Quark

Quarks are a type of elementary particle and major constituents of matter. They are the only particles in the Standard Model to experience all four fundamental interaction, which are also known as fundamental interactions....
s, antiquarks
Antiparticle

Corresponding to most kinds of particle physics, there is an associated antiparticle with the same mass and opposite electric charge. For example, the antiparticle of the electron is the positively charged antielectron, or positron, which is produced naturally in certain types of radioactive decay....
, and the gluon
Gluon

Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei....
s themselves.






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In particle physics, the strong interaction, or strong force, or color force, holds quark
Quark

Quarks are a type of elementary particle and major constituents of matter. They are the only particles in the Standard Model to experience all four fundamental interaction, which are also known as fundamental interactions....
s and gluon
Gluon

Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei....
s together to form proton
Proton

The proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H+....
s, neutron
Neutron

The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutrons are usually found in atomic nucleus....
s and other particles. The strong interaction is one of the four fundamental interaction
Fundamental interaction

In physics, a fundamental interaction or fundamental force is a process by which elementary particles interact with each other. An interaction is often described as a field , and is mediated by the exchange of gauge bosons between particles....
s, along with gravitation
Gravitation

Gravitation is a natural phenomenon that gives weight to objects. In everyday life, attraction due to gravity is the result of the presence of relatively large bodies, such as the Earth and the Moon....
, the electromagnetic force
Electromagnetic force

In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. It is the electromagnetic force that holds electrons and protons together in atoms, and which hold atoms together to make molecules....
 and the weak interaction
Weak interaction

The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
. The word strong is used since the strong interaction is the most powerful of the four fundamental forces; its typical field strength is 100 times the strength of the electromagnetic force
Electromagnetic force

In physics, the electromagnetic force is the force that the electromagnetic field exerts on electrically charged particles. It is the electromagnetic force that holds electrons and protons together in atoms, and which hold atoms together to make molecules....
, some 1013 times as great as that of the weak force, and about 1038 times that of gravitation.

The strong force is thought to be mediated by gluons, acting upon quark
Quark

Quarks are a type of elementary particle and major constituents of matter. They are the only particles in the Standard Model to experience all four fundamental interaction, which are also known as fundamental interactions....
s, antiquarks
Antiparticle

Corresponding to most kinds of particle physics, there is an associated antiparticle with the same mass and opposite electric charge. For example, the antiparticle of the electron is the positively charged antielectron, or positron, which is produced naturally in certain types of radioactive decay....
, and the gluon
Gluon

Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei....
s themselves. This is detailed in the theory of quantum chromodynamics
Quantum chromodynamics

Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons ....
 (QCD).

History

Before the 1970s, proton
Proton

The proton is a subatomic particle with an electric charge of +1 elementary charge. It is found in the nucleus of each atom but is also stable by itself and has a second identity as the hydrogen ion, H+....
s and neutron
Neutron

The neutron is a subatomic particle with no net electric charge and a mass slightly larger than that of a proton.Neutrons are usually found in atomic nucleus....
s were thought to be indivisible fundamental particles. It was known that protons carried a positive electrical charge, electric repulsion
Electromagnetism

Electromagnetism is the physics of the electromagnetic field, a field which exerts a force on Elementary particles with the property of electric charge and which is reciprocally affected by the presence and motion of such particles....
 made same-charge particles repel each other, and multiple protons were bound together in the atomic nucleus
Atomic nucleus

The nucleus of an atom is the very dense region, consisting of nucleons , at the center of an atom. Although the size of the nucleus varies considerably according to the mass of the atom, the size of the entire atom is comparatively constant....
. However, it was unknown what force held the like-charged protons together (with neutrons) in the nucleus.

Another, stronger, attractive force was postulated to explain how protons and neutrons were held together in the atomic nucleus, overcoming electromagnetic repulsion. For its high strength at short distances, it was dubbed the "strong" force. It was thought, at that time, this strong force was a fundamental force acting directly on the nuclear particles. Experiments suggested that the force acted equally between any nucleon
Nucleon

In physics, a nucleon is a collective name for two baryons: the neutron and the proton. They are constituents of the atomic nucleus and until the 1960s were thought to be elementary particles....
s, whether protons or neutrons.

It was later discovered this phenomenon was only a residual side-effect of another, truly fundamental, force acting directly on particles inside protons and neutrons, called quarks and gluons. This newly-discovered force was initially called the "color force." The name was chosen for convenience, and has no relation to visible color.

Today, the term "strong force" refers to the strong nuclear force that acts directly on quarks and gluons. The original strong force that acts between nucleons (and also between particles made of quarks, or hadron
Hadron

In particle physics, a hadron is a bound state of quarks. Hadrons are held together by the strong interaction, similarly to how molecules are held together by the electromagnetic force....
s) is today called the nuclear force
Nuclear force

The nuclear force is the force between two or more nucleons. It is responsible for binding of protons and neutrons into Atomic nucleus. To a large extent, this force can be understood in terms of the exchange of virtual light mesons, such as the pions....
, or the "residual strong nuclear force."

Details


The behavior of the strong force


The contemporary strong force is described by quantum chromodynamics
Quantum chromodynamics

Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons ....
 (QCD), a part of the standard model
Standard Model

The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
 of particle physics. Mathematically, QCD is a non-Abelian
Non-abelian

In theoretical physics, a non-abelian gauge transformation means a gauge transformation taking values in some group G, the elements of which do not obey the commutative law when they are multiplied....
 gauge theory
Gauge theory

In physics, gauge theory is a quantum field theory where the Lagrangian is invariant under certain transformations.The transformations form a Lie group which is referred to as the symmetry group or the gauge group of the theory....
 based on a local (gauge) symmetry group
Symmetry group

The symmetry group of an object is the group of all isometries under which it is invariant with Function composition as the operation. It is a subgroup of the isometry group of the space concerned....
 called SU(3).

Quarks and gluons are the only fundamental particles which carry non-vanishing color charge, and hence participate in strong interactions. The strong force itself acts directly only upon elementary quark and gluon particles.

All quarks and gluons in QCD interact with each other through the strong force. The strength of interaction is parametrized by the strong coupling constant
Coupling constant

In physics, a coupling constant, usually denoted g, is a number that determines the strength of an interaction. Usually the Lagrangian or the Hamiltonian mechanics of a system can be separated into a kinetic part and an interaction part....
. This strength is modified by the gauge color charge
Coupling constant

In physics, a coupling constant, usually denoted g, is a number that determines the strength of an interaction. Usually the Lagrangian or the Hamiltonian mechanics of a system can be separated into a kinetic part and an interaction part....
 of the particle, a group theoretical
Group theory

In mathematics and abstract algebra, group theory studies the algebraic structures known as group .The concept of a group is central to abstract algebra: other well-known algebraic structures, such as ring , field , and vector spaces can all be seen as groups endowed with additional operations and axioms....
 property which has nothing to do with ordinary visual color.

The strong force acting between quarks, unlike other forces, does not diminish in strength with increasing distance, after a limit (about the size of a hadron) has been reached. It remains at a strength of about 10 Newtons, no matter how far away from each other the particles are, after this limiting distance has been reached. In QCD, this phenomenon is called color confinement, implying that only hadrons can be observed; this is because the amount of work done against a force of 10 Newtons is enough to create particle-antiparticle pairs within a very short distance of an interaction. Evidence for this effect is seen in many failed free quark searches.

The elementary quark and gluon particles affected are unobservable directly, but instead emerge as jets of newly created hadrons, whenever energy is deposited into a quark-quark bond, as when a quark in a proton is struck by a very fast quark (in an impacting proton) during an accelerator experiment. However, quark-gluon plasma
Quark-gluon plasma

A quark-gluon plasma is a phase of quantum chromodynamics which exists at extremely high temperature and/or density. This phase consists of free quarks and gluons, which are the basic building blocks of matter....
s have been observed.

The behavior of the residual strong force (nuclear force)


A residual effect of the strong force is called the nuclear force
Nuclear force

The nuclear force is the force between two or more nucleons. It is responsible for binding of protons and neutrons into Atomic nucleus. To a large extent, this force can be understood in terms of the exchange of virtual light mesons, such as the pions....
. The nuclear force acts between hadron
Hadron

In particle physics, a hadron is a bound state of quarks. Hadrons are held together by the strong interaction, similarly to how molecules are held together by the electromagnetic force....
s, such as nucleon
Nucleon

In physics, a nucleon is a collective name for two baryons: the neutron and the proton. They are constituents of the atomic nucleus and until the 1960s were thought to be elementary particles....
s in atomic nuclei. This "residual strong force," acting indirectly, transmits gluons that form part of the virtual pi and rho mesons, which, in turn, transmit the nuclear force between nucleons.

The residual strong force is thus a minor residuum of the strong force which binds quarks together into protons and neutrons. This same force is much weaker between neutrons and protons, because it is mostly neutralized within them, in the same way that electromagnetic forces between neutral atoms (van der Waals forces) are much weaker than the electromagnetic forces that hold the atoms internally together.

Unlike the strong force itself, the nuclear force
Nuclear force

The nuclear force is the force between two or more nucleons. It is responsible for binding of protons and neutrons into Atomic nucleus. To a large extent, this force can be understood in terms of the exchange of virtual light mesons, such as the pions....
, or residual strong force, does diminish in strength, strongly with distance. The decrease is approximately as a negative exponential power of distance, though there is no simple expression known for this; see Yukawa potential
Yukawa potential

A Yukawa potential is a potential of the formHideki Yukawa showed in the 1930s that such a potential arises from the exchange of a massive scalar field such as the field of the pion whose mass is ....
. This fact, together with the less-rapid decrease of the disruptive electromagnetic force between protons with distance, causes the instability of larger atomic nuclei, such as all those with atomic number
Atomic number

In chemistry and physics, the atomic number is the number of protons found in the atomic nucleus of an atom. It is conventionally represented by the symbol Z....
s larger than 82.

See also

  • Binding energy
    Binding energy

    Binding energy is the mechanical energy required to disassemble a whole into separate parts. A bound system has a lower potential energy than its constituent parts; this is what keeps the system together....
  • Color charge
    Color charge

    In particle physics, color charge is a property of quarks and gluons which are related to their strong interactions in the context of quantum chromodynamics ....
  • Coupling constant
    Coupling constant

    In physics, a coupling constant, usually denoted g, is a number that determines the strength of an interaction. Usually the Lagrangian or the Hamiltonian mechanics of a system can be separated into a kinetic part and an interaction part....
  • Internucleon force and Nuclear physics
    Nuclear physics

    Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei.The most commonly known applications of nuclear physics are nuclear power and nuclear weapons, but the research field is also the basis for a far wider range of applications, including in the medical sector , in materials engineering...
  • Nuclear force
    Nuclear force

    The nuclear force is the force between two or more nucleons. It is responsible for binding of protons and neutrons into Atomic nucleus. To a large extent, this force can be understood in terms of the exchange of virtual light mesons, such as the pions....
  • QCD matter
    QCD matter

    Quark matter or QCD matter refers to any of a number of theorized phase of matter whose degrees of freedom include quarks and gluons. These theoretical phases would occur at extremely high temperatures and densities, billions of times higher than can be produced in equilibrium in laboratories....
  • Quantum field theory
    Quantum field theory

    Quantum field theory or QFT provides a theoretical framework for constructing quantum mechanics models of systems classically described by field or of Many-body problem....
     and Gauge theory
    Gauge theory

    In physics, gauge theory is a quantum field theory where the Lagrangian is invariant under certain transformations.The transformations form a Lie group which is referred to as the symmetry group or the gauge group of the theory....
  • Standard model
    Standard Model

    The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
     of particle physics and Standard model (basic details)
    Standard model (basic details)

    This is a detailed description of the Standard Model of particle physics. It describes how the leptons, quarks, gauge bosons and the Higgs boson fit together....
  • Weak interaction
    Weak interaction

    The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
    , electromagnetism
    Electromagnetism

    Electromagnetism is the physics of the electromagnetic field, a field which exerts a force on Elementary particles with the property of electric charge and which is reciprocally affected by the presence and motion of such particles....
     and gravity


Further reading



External links

  • (PDF
    Portable Document Format

    Portable Document Format is a file format created by Adobe Systems in 1993 for document exchange. PDF is used for representing two-dimensional documents in a manner independent of the application software, hardware, and operating system....
     file) by J.R. Christman for .
  • at CERN is the heavy ion collaboration that will investigate aspects of the Strong Nuclear Force upon the completion of the building of the Large Hadron Collider at CERN.
  • at the Relativistic Heavy Ion Collider at Brookhaven Nation Laboratory in New York, USA. Investigates many aspects of the Strong Nuclear Force including the theoretical Quark Gluon Plasma.