Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for a backward peak in the gamma+d->pi^0+d cross section near
  the eta threshold   High-quality cross sections for the reaction gamma+d->pi^0+d have been
measured using the CLAS at Jefferson Lab over a wide energy range near and
above the eta-meson photoproduction threshold. At backward c.m. angles for the
outgoing pions, we observe a resonance-like structure near E_gamma=700 MeV. Our
model analysis shows that it can be explained by eta excitation in the
intermediate state. The effect is the result of the contribution of the
N(1535)S_11 resonance to the amplitudes of the subprocesses occurring between
the two nucleons and of a two-step process in which the excitation of an
intermediate eta meson dominates.

25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat