Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Diffractive $\phi$-meson photoproduction on proton near threshold   Photoproduction of $\phi$-meson on protons was studied by means of linearly
polarized photons at forward angles in the low-energy region from threshold to
$E_{\gamma}$= 2.37 GeV. The differential cross sections at $t = -|t|_{min}$ do
not increase smoothly as $E_{\gamma}$ increases, but show a local maximum at
around 2.0 GeV. The angular distributions demonstrate that $\phi$-mesons are
photo-produced predominantly by helicity-conserving processes, and the local
maximum is not likely due to unnatural-parity processes.

36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
29
The categories of this paper are: funct-an
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
32
The categories of this paper are: atom-ph