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The down quark is a first-generation
Generation (particle physics)

In particle physics, a generation is a division of the elementary particles. Between generations, particles differ only by their mass. All fundamental interactions and quantum numbers are identical....
 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....
 with a charge of - e
Elementary charge

The elementary charge, usually denoted e, is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron....
. It is the second-lightest of all the six flavours
Flavour (particle physics)

In particle physics, flavour or flavor is a quantum number of elementary particles. In quantum chromodynamics flavour is a global symmetry....
 of quarks, the lightest being the up quark
Up quark

The up quark is a particle described by the Standard Model theory of physics. It is a first-generation quark with a charge of +elementary charge....
. Down quarks are most commonly found in nucleons (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); protons contains one down quark and two up quarks, while 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 contains two down quarks and one up quark.

Mass
The bare mass
Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
 of down quarks is not well determined, but probably lies between 3.5 and 6.0 MeV
MEV

MeV and meV are Multiple of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:...
/c
Speed of light

The speed of light in an free space is an important physical constant usually written as c, with a value of 299,792,458 metres per second....
2.






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The down quark is a first-generation
Generation (particle physics)

In particle physics, a generation is a division of the elementary particles. Between generations, particles differ only by their mass. All fundamental interactions and quantum numbers are identical....
 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....
 with a charge of - e
Elementary charge

The elementary charge, usually denoted e, is the electric charge carried by a single proton, or equivalently, the negative of the electric charge carried by a single electron....
. It is the second-lightest of all the six flavours
Flavour (particle physics)

In particle physics, flavour or flavor is a quantum number of elementary particles. In quantum chromodynamics flavour is a global symmetry....
 of quarks, the lightest being the up quark
Up quark

The up quark is a particle described by the Standard Model theory of physics. It is a first-generation quark with a charge of +elementary charge....
. Down quarks are most commonly found in nucleons (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); protons contains one down quark and two up quarks, while 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 contains two down quarks and one up quark.

Mass


The bare mass
Mass

In physical science, mass refers to the degree of acceleration a body acquires when subject to a force: bodies with greater mass are accelerated less by the same force....
 of down quarks is not well determined, but probably lies between 3.5 and 6.0 MeV
MEV

MeV and meV are Multiple of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:...
/c
Speed of light

The speed of light in an free space is an important physical constant usually written as c, with a value of 299,792,458 metres per second....
2. The down quark is very light compared to nucleons (~940 MeV/c2). The reason is that the majority of the mass of nucleons comes from the energy in 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....
 field
Field (physics)

In physics, a field is a physical quantity associated to each point of spacetime. A field can be classified as a scalar field, a vector field, or a tensor field, according to whether the value of the field at each point is a scalar , a vector , or, more generally, a tensor, respectively....
 holding the quarks together, and not the quark masses themselves.

Down quarks were theorized by Murray Gell-Mann
Murray Gell-Mann

Murray Gell-Mann is an United States physicist who received the 1969 Nobel Prize in physics for his work on the theory of particle physicss.Among his many accomplishments, he formulated the quark model of hadronic resonances, and identified the SU flavor symmetry of the light quarks, extending isospin to include strange quark, which he als...
 and George Zweig
George Zweig

George Zweig was originally trained as a particle physicist under Richard Feynman and later turned his attention to neurobiology. He spent a number of years as a Research Scientist at Los Alamos National Laboratory and MIT, but as of 2004, has gone on to work in the financial services industry....
 when they developed the quark model
Quark model

In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks, i.e., the quarks which give rise to the quantum numbers of the hadrons....
 in 1964 (Zweig called them aces rather than quarks), and the first evidence for them was found in deep inelastic scattering
Deep Inelastic Scattering

Deep inelastic scattering is the name given to a process used to probe the insides of hadrons , using electrons, muons and neutrinos. It provided the first convincing evidence of the reality of quarks, which up until that point had been considered by many to be a purely mathematical phenomenon....
 experiments at SLAC in 1968.

Hadrons containing down quarks

Some of the hadrons containing down quarks include:
  • Charged pion
    Pion

    In particle physics, a pion is any of three subatomic particles: , and . Pions are the lightest mesons and play an important role in explaining low-energy properties of the strong nuclear force....
    s are meson
    Meson

    In particle physics, mesons are subatomic particles composed of one quark and one antiquark. They are part of the hadron particle family ? particles made of quarks....
    s containing an up quark and an down antiquark, or vice versa.
  • Neutral pions is a linear combination
    Linear combination

    In mathematics, linear combinations are a concept central to linear algebra and related fields of mathematics.Most of this article deals with linear combinations in the context of a vector space over a field , with some generalisations given at the end of the article....
     of up quark-up antiquark and down quark-down antiquark, as are the and ? mesons.
  • The and flavorless
    Flavour (particle physics)

    In particle physics, flavour or flavor is a quantum number of elementary particles. In quantum chromodynamics flavour is a global symmetry....
     mesons are linear combinations of several quark-antiquark pairs, including down quark-down antiquark.
  • A large number of detected baryon
    Baryon

    Baryons are the family of composite particle subatomic particle made of three quarks, as opposed to the mesons which are the family of composite particles made of one quark and one antiquark....
    s contain one or more down quarks. Like the 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, the Delta baryon
    Delta baryon

    The Delta baryons are relatively light baryons made of only up and down quarks....
    s are made of only up and down quarks: the contains no down quark, but the contains one, the contains two, and the contains three.


See also

  • 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 of nucleons....
  • Quark model
    Quark model

    In physics, the quark model is a classification scheme for hadrons in terms of their valence quarks, i.e., the quarks which give rise to the quantum numbers of the hadrons....