Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Imaging the nucleus with high-energy photons   In the 1930's, nuclear physicists developed the first realistic atomic
models, showing that nuclei were made up of protons and neutrons. In the
1960's, Deep Inelastic Scattering experiments showed that protons and neutrons
had internal structure: quarks and gluons (collectively, partons), and later
experiments showed that the parton momentum distributions are different in
heavy nuclei, compared to those in free nucleons. This difference is not
surprising; partons are sensitive to their environment, and two gluons from
different nucleons may fuse together, for example.
  Understanding how quarks and gluons behave in the nuclear environment is a
significant focus of modern nuclear physics. Recent measurements have provided
us with an improved understanding of how quark and gluon densities are altered
in heavy nuclei. We have also begun to make multi-dimensional pictures of the
nucleus, exploring how these alterations are distributed within heavy nuclei.
We naturally expect these modifications to be largest in the core of a nucleus,
and smaller near its periphery; this can change the effective shape of the
nucleus. We have also started to explore the transverse momentum distribution
of the partons in the nuclei, and, using incoherent photoproduction as a probe,
study event-by-event fluctuations in nucleon and nuclei parton densities.
  This article will explore recent progress in measurements of nuclear
structure at high energy, with some emphasis on these multi-dimensional
pictures. We will also discuss how a future electron-ion collider (EIC) with
high luminosity and center-of-mass energy will make exquisitely detailed images
of partons in a nucleus.

23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
1
The categories of this paper are: cs
18
The categories of this paper are: econ
3
The categories of this paper are: physics
4
The categories of this paper are: cond-mat