Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Production of Highly Polarized Positron Beams via Helicity Transfer from
  Polarized Electrons in a Strong Laser Field   The production of a highly-polarized positron beam via nonlinear
Breit-Wheeler processes during the interaction of an ultraintense circularly
polarized laser pulse with a longitudinally spin-polarized ultrarelativistic
electron beam is investigated theoretically. A new Monte Carlo method employing
fully spin-resolved quantum probabilities is developed under the local constant
field approximation to include three-dimensional polarizations effects in
strong laser fields. The produced positrons are longitudinally polarized
through polarization transferred from the polarized electrons by the medium of
high-energy photons. The polarization transfer efficiency can approach 100\%
for the energetic positrons moving at smaller deflection angles. This method
simplifies the post-selection procedure to generate high-quality positrons in
further applications. In a feasible scenario, a highly polarized ($40\%-65\%$),
intense ($10^5$/bunch$-10^6 $/bunch), collimated ($5$mrad$-70$ mrad) positron
beam can be obtained in a femtosecond timescale. The longitudinally polarized
positron sources are desirable for applications in high-energy physics and
material science .

16
The categories of this paper are: stat
19
The categories of this paper are: eess
17
The categories of this paper are: q-fin
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci