Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The study of the negative pion production in neutron-proton collisions
  at beam momenta below 1.8 GeV/c   A detailed investigation of the reaction np -> pp\pi^{-} has been carried out
using the data obtained with the continuous neutron beam produced by charge
exchange scattering of protons off a deuterium target. A partial wave
event-by-event based maximum likelihood analysis was applied to determine
contributions of different partial waves to the pion production process. The
combined analysis of the np -> pp\pi^{-} and pp -> pp\pi^{0} data measured in
the same energy region allows us to determine the contribution of isoscalar
partial waves (I=0) in the momentum range from 1.1 up to 1.8 GeV/c. The decay
of isoscalar partial waves into (^1S_0)_{pp}\pi$ channel provides a good tool
for a determination of the pp S-wave scalar scattering length in the final
state which was found to be a_{pp}=-7.5\pm 0.3 fm.

34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
2
The categories of this paper are: math
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess