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The first EMC effect [1] shows that if the
quark deep inelastic data of heavier nuclei are
compared to those of the deuteron, then one finds that data
of the heavier nucleus are
located in a smaller x region. This property means that
the Fermi motion of quarks of a heavy nucleus is smaller
than that of the deuteron's quarks. Hence,
one conclusion inferred from the first EMC effect is the
increase of the self volume occupied by quarks in
nuclei together with the increase in number of nucleons A.
(Note that, excluding a very small
number of light nuclei, nucleon density of
nuclei practically takes the same value.)
The nucleus - liquid drop similarity of the regular monopole theory
easily explains this effect. Thus, in liquids (and in solids)
electrons of a neighboring atom (denoted by B) penetrate the volume
of the atom examined here (denoted by A). Thus, the attractive
field of the nucleus of A is partially screened by electrons
of B. Hence, electrons of A "see" a smaller attractive force and
settle in a larger volume. In nuclei, the first EMC effect is the magnetic
monopole analog of this effect: just replace the nucleus by the
baryonic core and the electrons by quarks.
The first EMC effect was discovered about a decade after the
formulation of QCD. In spite of this fact, proponents of
QCD did not predict this effect. Thus the first EMC effect is described
in its first report by the following words [1]: "The observed
x-dependence of this ratio is in disagreement with existing
theoretical predictions."
Moreover, an
acceptable explanation of the first EMC effect cannot be found in
standard QCD textbooks. The lack of an adequate QCD explanation
for this effect is stated in the literature [2].
Furthermore, a recent CERN publication declares:
the EMC data still puzzle QCD supporters. For details,
click here.
References:
[1] J. J. Aubert et al., Phys. Lett. B123, 275 (1983).
[2] J. Arrington et al., J. Phys. Conference Series, 69, 012024 (2007).
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