1,463 research outputs found
Angular distribution of high-energy photoproduction close to the end of spectrum
We consider the differential cross section of electron-positron pair
production by a high-energy photon in a strong Coulomb field close to the end
of the electron or positron spectrum. When the momentum transfer largely
exceeds the electron mass, the cross section is obtained analytically in a
compact form. Coulomb corrections essentially modify the cross section even for
moderate values of the nuclear charge number . In the same kinematical
region, the angular distribution for bound-free pair production,
bremsstrahlung, and photorecombination is also obtained.Comment: 12 pages, 4 figure
High-energy photoproduction cross section close to the end of spectrum
We consider the cross section of electron-positron pair production by a
high-energy photon in a strong Coulomb field close to the end of electron or
positron spectrum. We show that the cross section essentially differs from the
result obtained in the Born approximation as well as form the result which
takes into account the Coulomb corrections under assumption that both electron
and positron are ultrarelativistic. The cross section of bremsstrahlung in a
strong Coulomb field by a high-energy electron is also obtained in the region
where the final electron is not ultrarelativistic.Comment: 20 pages, 4 figure
The Induced Charge Generated By The Potential Well In Graphene
The induced charge density, , generated in graphene by the
potential well of the finite radius is considered. The result for
is derived for large distances . We also obtained
the induced charges outside of the radius and inside of this radius
for subcritical and supercritical regimes. The consideration is based on the
convenient representation of the induced charge density via the Green's
function of electron in the field.Comment: 12 pages, 2 figures, version published in Phys.Rev.
Screening of Coulomb Impurities in Graphene
We calculate exactly the vacuum polarization charge density in the field of a
subcritical Coulomb impurity, , in graphene. Our analysis is based on
the exact electron Green's function, obtained by using the operator method, and
leads to results that are exact in the parameter , where is
the "fine structure constant" of graphene. Taking into account also
electron-electron interactions in the Hartree approximation, we solve the
problem self-consistently in the subcritical regime, where the impurity has an
effective charge , determined by the localized induced charge. We find
that an impurity with bare charge Z=1 remains subcritical, , for any , while impurities with and higher can become
supercritical at certain values of .Comment: 4 pages, 2 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
Ultrarelativistic quasiclassical wave functions in strong laser and atomic fields
The problem of an ultrarelativistic charge in the presence of an atomic and a
plane-wave field is investigated in the quasiclassical regime by including
exactly the effects of both background fields. Starting from the quasiclassical
Green's function obtained in [Phys. Lett. B \textbf{717}, 224 (2012)], the
corresponding in- and out-wave functions are derived in the experimentally
relevant case of the particle initially counterpropagating with respect to the
plane wave. The knowledge of these electron wave functions opens the
possibility of investigating a variety of problems in strong-field QED, where
both the atomic field and the laser field are strong enough to be taken into
account exactly from the beginning in the calculations.Comment: 24 pages, no figure
Coulomb effects in high-energy electroproduction by a heavy charged particles in an atomic field
The cross section of high-energy pair production by a heavy charged
particle in the atomic field is investigated in detail. We take into account
the interaction with the atomic field of pair and a heavy particle as
well. The calculation is performed exactly in the parameters of the atomic
field. It is shown that, in contrast to the commonly accepted point of view,
the cross section differential with respect to the final momentum of a heavy
particle is strongly affected by the interaction of a heavy particle with the
atomic field. However, the cross section integrated over the final momentum of
a heavy particle is independent of this interaction.Comment: 10 pages, 4 figure
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