Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pion - Nucleon Bremsstrahlung beyond the Soft-Photon approximation   A dynamical model based on effective Lagrangians is proposed to describe the
bremsstrahlung reaction $ \pi N \to \pi N \gamma$ at low energies. The
$\Delta(1232)$ degrees of freedom are incorporated in a way consistent with
both, electromagnetic gauge invariance and invariance under contact
transformations. The model also includes the initial and final state
rescattering of hadrons via a T-matrix with off the momentum-shell effects. The
double differential distribution of photons is computed for three different
T-matrix models and the results are compared with the soft photon
approximation, and with experimental data. The aim of this analysis is to test
the off-shell behaviour of the different T-matrices under consideration.
Finally an alternative simpler dynamical model that incorporates the unstable
character of the isobar-$\Delta(1232)$ through a complex mass, is presented. As
we will see it is suitable for the study of the magnetic moment of the
resonance.

31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph