Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extraction of a_nn from pi- d -> n n gamma   I present a calculation of the pi- d -> n n gamma reaction to third order in
chiral perturbation theory. The short-distance physics of this reaction can be
constrained by relating it to several important low-energy weak reactions. The
theoretical error in a_nn extracted from this reaction can thus be reduced by a
factor larger than three to +-0.05 fm.

33
The categories of this paper are: plasm-ph
24
The categories of this paper are: dg-ga
27
The categories of this paper are: comp-gas
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
29
The categories of this paper are: funct-an
37
The categories of this paper are: supr-con
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
10
The categories of this paper are: q-bio