306 research outputs found
QCD sum rules as a tool for investigation of the baryon properties at finite densities
We analyse the calculations of deep inelastic structure functions of free
nucleons by QCD sum rules method,carried out by others.We present our results
of calculation of the distribution of valence quarks in nucleon placed into the
nuclear matter.We show that the change in distribution has typical EMC shape.We
discuss possible application of the method to investigation of other aspects of
deep-inelastic processes.We analyse also the limits of possibilities of the
approach.Comment: 4 pages, LaTeX, no figure
Finite density QCD sum rules for nucleons
It is shown how the QCD sum rules can be applied for the investigation of the
density dependence of the nucleon parameters. These characteristics can be
expressed through the expectation values of QCD operators in nuclear matter. In
certain approximations the expectation values are related to the observables.
First applications of the approach reproduced some of the basic features of
nuclear physics, providing also a new knowledge. The program of the future work
is presented. The difficulties of the approach are discussed.Comment: 22 pages, Lecture at the International School on Nuclear Physics,
Erice,200
Compatibility of QCD sum-rules and Hadron field theory in a dense medium
The compatibility of the QCD sum rules and effective hadronic models
predictions are examined. For this purpose we have considered the results for
the nucleon self-energy in a dense hadronic environment provided by two
independent QCD sum-rules calculations. They are immersed in a theory of
hadronic fields giving rise to non-linear interactions, whose vertices are
parameterized in different ways. Although all of them reproduce the self-energy
used as input, very different descriptions of nuclear observables are obtained.
Only under very definite circumstances we have found an acceptable agreement
with the nuclear matter properties. To achieve this, phenomenological
parameters are not required at all.Comment: 8 pages, 2 figure
Nucleon QCD sum rules in nuclear matter including radiative corrections
We calculate the nucleon parameters in nuclear matter using the QCD sum rules
method. The radiative corrections to the leading operator product expansion
terms are included, with the corrections of the order \alpha_s beyond the
logarithmic approximation taken into account. The density dependence of the
influence of radiative corrections on the nucleon parameters is obtained. At
saturation density the radiative corrections increase the values of vector and
scalar self-energies by about 40 MeV, and 30 MeV correspondingly. The results
appear to be stable with respect to possible variations of the value of
\Lambda_{QCD}.Comment: 16 pages, 2 figure
Asymptotic behavior of photoionization cross section in a central field
We demonstrate that the high energy nonrelativistic asymptotic for the
photoionization cross section in a central field can be expressed in
terms of the asymptotic of the Fourier transform of the field. We show
that the cross sections drop in the same way for the fields with the Coulomb
short distance behavior. The character of the cross sections energy behavior is
related to the analytical properties of the function . The cross sections
exhibit power drop for the potentials which have singularities an the real
axis. They suffer the exponential drop if has singularities in the
complex plane.Comment: 11 page
Asymptotic behavior of photoionization cross section in a central field. Ionization of the states
We continue our studies of the high energy nonrelativistic asymptotics for
the photoionization cross section of the systems bound by a central field
. We consider the bound states with the orbital momentum . We
show, that as well as for the states the asymptotics can be obtained
without solving of the wave equations for the bound and outgoing electrons. The
asymptotics of the cross sections is expressed in terms of the asymptotics of
the Fourier transform of the field and its derivative by
employing the Lippmann--Schwinger equation. The shape of the energy dependence
of the cross sections is determined by the analytical properties of the
potential . The cross sections exhibit power drop with the increase of
the photon energy for the potentials which have singularities on the
real axis. They experience exponential drop if has poles in the complex
plane. We trace the energy dependence of the ratios of the photoionization
cross sections for and electrons from the states with the same
principle quantum number. We apply the results to the physics of fullerenes.Comment: 14 page
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