Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An explanation of the ABC enhancement in the dd -> alpha X reaction at
  intermediate energies   The dd -> alpha X reaction is studied in a model where each pair of nucleons
in the projectile and target deuterons undergoes pion production through the NN
-> d pi reaction. The condition that the two deuterons fuse to form an
alpha-particle then leads to peaks at small missing masses, the well-known ABC
enhancement, but also a broad structure around the maximum missing mass. With a
simplified input amplitude the model gives a quantitative description of both
the alpha-particle momentum and angular distributions for a deuteron beam
energy of 1250 MeV.

23
The categories of this paper are: solv-int
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
3
The categories of this paper are: physics
2
The categories of this paper are: math
18
The categories of this paper are: econ
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci