Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Identification of Observables for Quark and Gluon Orbital Angular
  Momentum   A new debate has recently arisen on the subject of orbital angular momentum
in QCD, in particular on its observability and on its partonic interpretation.
Orbital momentum can be defined in QCD using two different decomposition
schemes that yield a kinetic and a canonical definition, respectively. We argue
that kinetic orbital angular momentum is intrinsically associated with twist
three generalized parton distributions, and it is therefore more readily
observable, while, due to parity constraints, canonical angular momentum, if
defined as suggested in the literature in terms of generalized transverse
momentum distributions, cannot be observed in scattering processes involving a
single hadronic reaction plane.

11
The categories of this paper are: hep-lat
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
23
The categories of this paper are: solv-int
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
35
The categories of this paper are: mtrl-th
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
31
The categories of this paper are: ao-sci