Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electromagnetic form factors of the nucleon   Elastic form factors provide information about the low energy structure of
composite particles.Recent double polarization coincidence experiments
significantly improved our knowledge of proton and neutron form factors. Recoil
polarization measurements in the p(\vec e, e' \vec p) reaction proved that at
momentum transfers above Q^2 \simeq 1.5 (GeV/c)^2 the electric form factor of
the proton falls significantly faster than the dipole expectation. The
close--to--dipole shape at low Q^2 of the neutron magnetic form factor is now
confirmed by independent measurements. For the neutron electric form factor
\vec ^3He(\vec e,e'n), \vec D(\vec e,e'n) and D (\vec e,e' \vec n) double
polarization experiments have provided model independent results, within their
statistical errors in agreement with the Galster parameterization.

16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph