Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resonant photoproduction of high-energy electron-positron pairs in the
  field of a nucleus and a plane electromagnetic wave   The resonant photoproduction of ultrarelativistic electron-positron pairs
(PPP) in a nuclear field and a weak laser field is theoretically studied. Under
resonance conditions, the intermediate virtual electron (positron) in the laser
field becomes a real particle. As a result, the initial process of the second
order in the fine structure constant in the laser field effectively reduces
into two successive processes of the first order: single-photon production of
electron-positron pair in a laser field (laser-stimulated Breit-Wheeler
process) and laser-assisted process of electron (positron) scattering on a
nucleus. Resonant kinematics of PPP is studied in details. It is shown that for
the considered laser intensities resonance is possible only for the initial
photon energies greater than the characteristic threshold energy. At the same
time, the ultrarelativistic electron and positron propagate in a narrow cone
along the direction of the initial photon momentum. The resonant energy of the
positron (electron) can has two values for each radiation angle which varies
from zero to some maximum value determined by the energy of the initial photon
and the threshold energy. Resonant differential cross section of the studied
process was obtained. It is shown that the resonant differential cross section
of the PPP can significantly exceed the corresponding cross section of the PPP
without an external field. The project calculations may be experimentally
verified by the scientific facilities of pulsed laser radiation (SLAC, FAIR,
XFEL, ELI, XCELS)

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The categories of this paper are: funct-an
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The categories of this paper are: plasm-ph
4
The categories of this paper are: cond-mat
2
The categories of this paper are: math
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The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
31
The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: q-alg
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys