Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New estimation for neutron-neutron scattering length: charge symmetry
  and charge independence breaking revisited   Recent experimental results for neutron-neutron scattering length are
reanalyzed from the point of view of three-nucleon force contribution. We found
that the limiting value of $a_{nn}=- 15.8\pm 0.5$~fm must be free of any
implicit three-body force contribution. We have also shown that the difference
between the above experimental value of $a_{nn}$ and the well established value
of neutron-proton scattering length $a_{np}$ can be explained by differences in
the one-pion exchange potentials.

36
The categories of this paper are: cmp-lg
7
The categories of this paper are: hep-th
2
The categories of this paper are: math
18
The categories of this paper are: econ
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
31
The categories of this paper are: ao-sci
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th