Color-glass condensate

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Color-glass condensate (CGC) is a type of

gluons
that have very small momenta, or more precisely a very small
Bjorken scaling
variable. The small momenta gluons dominate the description of the collision because their density is very large. This is because a high-momentum gluon is likely to split into smaller momentum gluons. When the gluon density becomes large enough, gluon-gluon recombination puts a limit on how large the gluon density can be. When gluon recombination balances gluon splitting, the density of gluons saturate, producing new and universal properties of hadronic matter. This state of saturated gluon matter is called the color-glass condensate.[1]

"Color" in the name "color-glass condensate" refers to a type of charge that

silica and other materials that are disordered and act like solids on short time scales but liquids on long time scales. In the CGC phase
, the gluons themselves are disordered and do not change their positions rapidly. "Condensate" means that the gluons have a very high density.

The color-glass condensate describes an

The color-glass condensate is important because it is proposed as a universal form of matter that describes the properties of all high-energy, strongly interacting particles. It has simple properties that follow from first principles in the theory of strong interactions, quantum chromodynamics. It has the potential to explain many unsolved problems such as how particles are produced in high-energy collisions, and the distribution of matter itself inside of these particles.

Researchers at CERN believe they have created color-glass condensates during collisions of

ions. In these sorts of collisions, the standard outcome is that new particles are created and fly off in different directions. However, the Compact Muon Solenoid (CMS) team at the LHC found that in a sample of 2 million lead-proton collisions, some pairs of particles flew away from each other with their respective directions correlated.[2]
This correlation of directions is the anomaly that might be caused by the existence of a color-glass condensate while the particles are colliding.

Erroneous description in term of hadronic pancakes or gluonic wall

The high density of gluon seen during the collision is often explained by

motion and as a result, the gluons inside the nucleus would appear to a stationary observer as a "gluonic wall" traveling near the speed of light. At very high energies, the density of the gluons in this wall would then increase greatly. However, this description is incorrect for two reasons:[4]

  1. Such description depends on the
    fundamental description using fictitious forces such as the Coriolis force
    .
  2. Penrose–Terrell effect
    .

A correct description of the collision can be given using light-front wave functions,[5][6] which are frame-independent.

See also

  • Glasma

References

  1. S2CID 118675789
    .
  2. ^ .
  3. ^ A. Accardi et al., “Electron Ion Collider: The Next QCD Frontier - Understanding the glue that binds us all,” 2012.
  4. ^ [S. J. Brodsky (2015) “Novel Perspectives from Light-Front QCD, Super-Conformal Algebra, and Light-Front Holography”] Bled Workshops Phys. 16 (2015) 2, 35-46 [arXiv:1512.05100]
  5. ^ P. A. M. Dirac, (1949) “Forms of Relativistic Dynamics” Rev. Mod. Phys. 21, 392-399
  6. ^ [S. J. Brodsky, H. C. Pauli and S. S. Pinsky, (1998) "Quantum chromodynamics and other field theories on the light cone" Phys. Rep. 301 299-486 [arXiv:hep-ph/9705477]

External links