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The number and momentum distribution of the gluons in the proton (gluon density) have been measured by two experiments, H1 and ZEUS, [23] in the years 1996–2007. The gluon contribution to the proton spin has been studied by the HERMES experiment at HERA. [24] The gluon density in the proton (when behaving hadronically) also has been measured ...
A hadron is a composite subatomic particle.Every hadron must fall into one of the two fundamental classes of particle, bosons and fermions. In particle physics, a hadron (/ ˈ h æ d r ɒ n / ⓘ; from Ancient Greek ἁδρός (hadrós) ' stout, thick ') is a composite subatomic particle made of two or more quarks held together by the strong interaction.
Quark-gluon plasma hadronization occurred shortly after the Big Bang when the quark–gluon plasma cooled down to the Hagedorn temperature (about 150 MeV) when free quarks and gluons cannot exist. [4] In string breaking new hadrons are forming out of quarks, antiquarks and sometimes gluons, spontaneously created from the vacuum. [5]
The gluon content of a hadron can be inferred from DIS measurements. Again, not all of the QCD binding energy is gluon interaction energy, but rather, some of it comes from the kinetic energy of the hadron's constituents. [3] Currently, the total QCD binding energy per hadron can be estimated through a combination of the factors mentioned.
The vector symmetry, U B (1) corresponds to the baryon number of quarks and is an exact symmetry. The axial symmetry U A (1) is exact in the classical theory, but broken in the quantum theory, an occurrence called an anomaly. Gluon field configurations called instantons are closely related to this anomaly.
For example, the hadron constituents of atomic nuclei, neutrons and protons, have charges of 0 e and +1 e respectively; the neutron is composed of two down quarks and one up quark, and the proton of two up quarks and one down quark. [12]
Photons with high photon energy can transform in quantum mechanics to lepton and quark pairs, the latter fragmented subsequently to jets of hadrons, i.e. protons, pions, etc.At high energies E the lifetime t of such quantum fluctuations of mass M becomes nearly macroscopic: t ≈ E/M 2; this amounts to flight lengths as large as one micrometer for electron pairs in a 100 GeV photon beam, while ...
The model indicates that "strings" of low-energy gluons will form most strongly between the quarks and the high-energy gluons, and that the "breaking" of these strings into new quark–antiquark pairs (part of the hadronization process) will result in some "stray" hadrons between the jets (and in the same plane). Since the quark-gluon ...