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Encyclopedia > Quarkonium

In high energy physics, a quarkonium (pl. quarkonia) is a flavorless meson constituted by the association of a quark and its own antiquark, such as the charmonium or the bottomonium. Examples of quarkonia are the J/ψ (which is a charmonium state) and the Υ (a bottomonium state). Because of the high mass of the top quark, a toponium does not exist, since the quark decays through its electroweak interaction before the bound state can form. Mesons made in the same way with the light quarks are usually not called quarkonia. This is partly because they mix among themselves. Particle physics is a branch of physics that studies the elementary constituents of matter and radiation, and the interactions between them. ... In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... The title given to this article is incorrect due to technical limitations. ... The top quark is a third-generation quark with a charge of +2/3. ... In physics, the electroweak theory presents a unified description of two of the four fundamental forces of nature: electromagnetism and the weak nuclear force. ... Quarks are one of the two basic constituents of matter in the Standard Model of particle physics. ...


Because of the large seperation in masses between the charm, bottom and the remaining quarks, the charmonium and bottomonium families do not mix with each other, or with the other flavourless mesons. For other uses of this term, see: Quark (disambiguation) 1974 discovery photograph of a possible charmed baryon In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... For other uses of this term, see: Quark (disambiguation) 1974 discovery photograph of a possible charmed baryon In particle physics, the quarks are subatomic particles thought to be elemental and indivisible. ... Quarks are one of the two basic constituents of matter in the Standard Model of particle physics. ... Flavour (or flavor) is a quantum number of elementary particles related to their weak interactions. ...

Contents


Charmonium states

In the following table, the same particle can be named with the spectroscopic notation or with its mass. In some cases excitation series are used: Ψ' is the first excitation of Ψ (for historical reasons, this one is called J/ψ particle); Ψ" is a second excitation, and so on. That is, names in the same cell are synonymous.


Some of the states are predicted, but have not been identified; others are unconfirmed. Particle X(3872) quantum numbers are unknown; its identity is debated. It may be:

  • a candidate for the 13D2 state;
  • a charmonium hybrid state;
  • a molecule.

Breaking news (July 6 2005): Y(4260) discovered during the BaBar experiment. See announcement. At first analysis it appears to be a charmonium state. But could be a D "molecule" or a 4-quark construct. In the field of particle physics BaBar is an international collaboration of more than 550 physicists and engineers investigating CP-violation effects using the BaBar particle detector at the Stanford Linear Accelerator, Stanford, CA, USA. If the CP symmetry holds, the decay rate of B meson particles and their anti...

Term symbol IG(JPC) Particle mass (MeV)
11S0 0+(0−+) ηc(1S), or ηc(2980) 2979.6±1.2
13S1 0(1−−) J/ψ(1S) 3096.916±0.011
11P1 0(1+−) hc(1P) 3526.2*
13P0 0+(0++) χc0(1P) 3415.2
13P1 0+(1++) χc1(1P) 3510.5
13P2 0+(2++) χc2(1P) 3556.3
21S0 0+(0−+) ηc(2S), or 3654*
23S1 0(1−−) ψ(3686) 3686.093±0.034
11D2 0+(2−+) ηc2(1D)
13D1 0(1−−) ψ(3770) 3770.0±2.4
13D2 0(2−−) ψ(3836) 3836±13
13D3 0(3−−) ψ3(1D)
21P1 0(1+−) hc(2P)
23P0 0+(0++) χc0(2P)
23P1 0+(1++) χc1(2P)
23P2 0+(2++) χc2(2P)
 ???? 0?(??) X(3872) 3872.0

Notes: The title given to this article is incorrect due to technical limitations. ...

* Needs confirmation.
Predicted, but not yet identified.
Candidate. Confirmation needed.
Interpretation as a 1−− charmonium state not favored.

Bottomonium states

In the following table, the same particle can be named with the spectroscopic notation or with its mass.


Some of the states are predicted, but have not been identified; others are unconfirmed.

Term symbol IG(JPC) Particle mass (MeV)
11S0 0+(0−+) ηb(1S)* 9300±20
13S1 0(1−−) Υ(1S) 9460.3
11P1 0(1+−) hb(1P)
13P0 0+(0++) χb0(1P) 9859.0±1.0
13P1 0+(1++) χb1(1P) 9892.7
13P2 0+(2++) χb2(1P) 9912.6
21S0 0+(0−+) ηb(2S)
23S1 0(1−−) Υ(2S) 10023.26
11D2 0+(2−+) ηb2(1D)
13D1 0(1−−) Υ(1D)
13D2 0(2−−) Υ2(1D)
13D3 0(3−−) Υ3(1D)
21P1 0(1+−) hb(2P)
23P0 0+(0++) χb0(2P) 10 232.1
23P1 0+(1++) χb1(2P) 10 255.2
23P2 0+(2++) χb2(2P) 10 268.5
33S1 0(1−−) Υ(3S) 10 355.2
43S1 0(1−−) Υ(4S) or Υ(10580) 10 580.0
53S1 0(1−−) Υ(10860) 10 865
63S1 0(1−−) Υ(11020) 11 0219

Notes:

* Preliminary results. Confirmation needed.

QCD and quarkonia

The computation of the properties of mesons in Quantum chromodynamics (QCD) is a fully non-perturbative one. As a result, the only general method available in a lattice QCD computation. However, there might be some simplification for the heavy quarkonia. In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... Quantum chromodynamics (QCD) is the theory describing one of the fundamental forces, the strong interaction. ... Lattice Quantum Chromodynamics (Lattice QCD) is the theory of quarks and gluons formulated on a space-time lattice. ...


The light quarks in a meson move at relativistic speeds, since the mass of the bound state is much larger than the mass of the quark. However, the charm and the bottom quarks in their quarkonia move relatively slowly. It is estimated that the speed, v, is 0.3 times the speed of light for charm and 0.1 times the speed of light for bottom. It is then possible to approximate the computation as an expansion in powers of v. This is called non-relativistic QCD (NRQCD). Albert Einsteins theory of relativity is a set of two theories in physics: special relativity and general relativity. ...


NRQCD has also been quantized as a lattice gauge theory. This makes the computation of quarkonium properties somewhat simpler. Good agreement with the bottomonium masses has been found. Indeed this provides one of the best controlled non-perturbative tests of QCD. For the charm family the agreement is not as good. Presumably v is not small enough for NRQCD to be accurate. Lattice gauge theory is a method to deal with gauge theory that is useful for computer-assisted calculations. ...


Disappearance of quarkonia has been suggested as a diagnostic of the formation of the quark-gluon plasma in experiments. Quark gluon plasma is a phase of Quantum Chromodynamics (QCD) which exists at extremely high temperature and density. ...


See also



In particle physics, a meson is a strongly interacting boson, that is, it is a hadron with integral spin. ... The title given to this article is incorrect due to technical limitations. ... Lattice Quantum Chromodynamics (Lattice QCD) is the theory of quarks and gluons formulated on a space-time lattice. ... Quantum chromodynamics (QCD) is the theory describing one of the fundamental forces, the strong interaction. ...

Particles in Physics - Composite particles
Molecules | Atoms | Atomic nuclei | Hadrons | Baryons | Mesons | Exotic baryons
Exotic mesons | Tetraquarks | Pentaquarks | Hyperons | Hybrids

  Results from FactBites:
 
Quarkonium Quantum Mechanics (1011 words)
This so-called quarkonium system might then be interpreted according to the familiar rules of nonrelativistic quantum mechanics using a potential to describe the interquark force.
Another observable, the square of the charmonium wave function at the origin, is measured by the leptonic decay widths of the spin-one levels where the quark and antiquark have their spins pointing in the same direction.
In the quarkonium picture, the decay of a vector (spin one, negative parity) meson into a lepton pair is described by the annihilation of the quarks into a virtual photon, which subsequently decays into the lepton pair.
Quarkonium - Wikipedia, the free encyclopedia (843 words)
In particle physics, quarkonium (pl. quarkonia) designates a flavorless meson whose constituents are a quark and its own antiquark.
This usage is because the lighter quarks (up, down, and strange) have very similar masses, compared to the heavier quarks, and so the physical states actually seen in experiments are quantum mechanical mixtures of the light quark states.
In this technique, one uses the fact that the motion of the quarks that comprise the quarkonium state is non-relativistic to assume that they move in a static potential, much like non-relativistic models of the hydrogen atom.
  More results at FactBites »

 
 

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