Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Energy dependence of the proton geometry in exclusive vector meson
  production   The gluon radius of the proton is expected to increase at small gluon
momentum fractions $x$, an effect which has hitherto not been considered in the
dipole model framework. We investigate the energy dependence of exclusive
$J/\psi$, $\phi$, and $\rho$ production by introducing three models for $x$
dependence of the gluon thickness function. We allow the transverse width of
the proton to increase as $x$ decreases, using a novel parametrisation in the
spherical proton and the hotspot model. We compare these with a model in which
the number of hotspots increases as $x$ decreases and confront the models with
HERA data. The models exhibit clear differences in the slope of the $t$-spectra
as well as in the cross-section ratios between coherent and incoherent events.
The data shows a preference for models in which the proton's size increases as
$x$ decreases.

4
The categories of this paper are: cond-mat
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
5
The categories of this paper are: gr-qc