Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Production of highly-polarized positrons using polarized electrons at
  MeV energies   The Polarized Electrons for Polarized Positrons experiment at the injector of
the Continuous Electron Beam Accelerator Facility has demonstrated for the
first time the efficient transfer of polarization from electrons to positrons
produced by the polarized bremsstrahlung radiation induced by a polarized
electron beam in a high-$Z$ target. Positron polarization up to 82\% have been
measured for an initial electron beam momentum of 8.19~MeV/$c$, limited only by
the electron beam polarization. This technique extends polarized positron
capabilities from GeV to MeV electron beams, and opens access to polarized
positron beam physics to a wide community.

20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat