2,132 research outputs found
Corrections to the energy levels of a spin-zero particle bound in a strong field
Formulas for the corrections to the energy levels and wave functions of a
spin-zero particle bound in a strong field are derived. General case of the sum
of a Lorentz-scalar potential and zero component of a Lorentz-vector potential
is considered. The forms of the corrections differ essentially from those for
spin-1/2 particles. As an example of application of our results, we evaluated
the electric polarizability of a ground state of a spin-zero particle bound in
a strong Coulomb field.Comment: 7 pages, 1 figur
Angular distributions in decays
The differential decay rates of the processes and
close to the threshold are calculated with
the help of the optical potential. The same calculations are made
for the decays of . We use the potential which has been suggested to
fit the cross sections of scattering together with and
six pion production in annihilation close to the
threshold. The invariant mass spectra is in agreement with the
available experimental data. The anisotropy of the angular distributions, which
appears due to the tensor forces in the interaction, is predicted
close to the threshold. This anisotropy is large enough to be
investigated experimentally. Such measurements would allow one to check the
accuracy of the model of interaction.Comment: 10 pages, 8 figure
Quasiclassical Green function in an external field and small-angle scattering
The quasiclassical Green functions of the Dirac and Klein-Gordon equations in
the external electric field are obtained with the first correction taken into
account. The relevant potential is assumed to be localized, while its spherical
symmetry is not required. Using these Green functions, the corresponding wave
functions are found in the approximation similar to the Furry-Sommerfeld-Maue
approximation. It is shown that the quasiclassical Green function does not
coincide with the Green function obtained in the eikonal approximation and has
a wider region of applicability. It is illustrated by the calculation of the
small-angle scattering amplitude for a charged particle and the forward photon
scattering amplitude. For charged particles, the first correction to the
scattering amplitude in the non-spherically symmetric potential is found. This
correction is proportional to the scattering angle. The real part of the
amplitude of forward photon scattering in a screened Coulomb potential is
obtained.Comment: 20 pages, latex, 1 figur
Charge asymmetry in high-energy photoproduction in the electric field of a heavy atom
The charge asymmetry in the differential cross section of high-energy
photoproduction in the electric field of a heavy atom is obtained.
This asymmetry arises due to the Coulomb corrections to the amplitude of the
process (next-to-leading term with respect to the atomic field). The deviation
of the nuclear electric field from the Coulomb field at small distances is
crucially important for the charge asymmetry. Though the Coulomb corrections to
the total cross section are negligibly small, the charge asymmetry is
measurable for selected final states of and . We further discuss
the feasibility for experimental observation of this effect.Comment: 6 pages, 3 figure
High-energy expansion of Coulomb corrections to the e+e- photoproduction cross section
First correction to the high-energy asymptotics of the total
photoproduction cross section in the electric field of a heavy atom is derived
with the exact account of this field. The consideration is based on the use of
the quasiclassical electron Green function in an external electric field. The
next-to-leading correction to the cross section is discussed. The influence of
screening on the Coulomb corrections is examined in the leading approximation.
It turns out that the high-energy asymptotics of the corresponding correction
is independent of the photon energy. In the region where both produced
particles are relativistic, the corrections to the high-energy asymptotics of
the electron (positron) spectrum are derived. Our results for the total cross
section are in good agreement with experimental data for photon energies down
to a few . In addition, the corrections to the bremsstrahlung spectrum are
obtained from the corresponding results for pair production.Comment: 22 pages, 7 figures, RevTeX.Typos are corrected. The numerical
results, figures and conclusions remain unchanged as they were obtained using
correct formula
Delbruck scattering and the g-factor of a bound electron
The leading contribution of the light-by-light scattering effects to g-factor
of a bound electron is derived. The corresponding amplitude is expressed in
terms of low-energy Delbruck scattering of a virtual photon. The result reads
Delta g = (7/216) alpha (Z alpha)^5
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