Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Isospin breaking in pion-deuteron scattering and the pion-nucleon
  scattering lengths   In recent years, high-accuracy data for pionic hydrogen and deuterium have
become the primary source of information on the pion-nucleon scattering
lengths. Matching the experimental precision requires, in particular, the study
of isospin-breaking corrections both in pion-nucleon and pion-deuteron
scattering. We review the mechanisms that lead to the cancellation of
potentially enhanced virtual-photon corrections in the pion-deuteron system,
and discuss the subtleties regarding the definition of the pion-nucleon
scattering lengths in the presence of electromagnetic interactions by comparing
to nucleon-nucleon scattering. Based on the pi^{+/-} p channels we find for the
virtual-photon-subtracted scattering lengths in the isospin basis
a^{1/2}=(170.5 +/- 2.0) x 10^{-3} mpi^{-1} and a^{3/2}=(-86.5 +/- 1.8) x
10^{-3} mpi^{-1}.

35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
7
The categories of this paper are: hep-th
20
The categories of this paper are: acc-phys
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
3
The categories of this paper are: physics
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
2
The categories of this paper are: math