Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Elastic Meson Production - Factorisation and Gauge Invariance   The factorisation of the hard amplitude for exclusive meson production in
deep inelastic scattering is considered in the framework of a simple model. It
is demonstrated explicitly how gauge invariance ensures the cancellation of
non-factorising contributions.

32
The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
37
The categories of this paper are: supr-con
4
The categories of this paper are: cond-mat
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga