Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The spin-dependent nd scattering length - a proposed high-accuracy
  measurement   The understanding of few-nucleon systems at low energies is essential, e.g.
for accurate predictions of element abundances in big-bang and stellar fusion.
Novel effective field theories, taking only nucleons, or nucleons and pions as
explicit degrees of freedom, provide a systematic approach, permitting an
estimate of theoretical uncertainties. Basic constants parameterising the short
range physics are derived from only a handful of experimental values. The
doublet neutron scattering length a_2 of the deuteron is particularly sensitive
to a three-nucleon contact interaction, but experimentally known with only 6%
accuracy. It can be deduced from the two experimentally accessible parameters
of the nd scattering length. We plan to measure the poorly known "incoherent"
nd scattering length a_{i,d} with 10^{-3} accuracy, using a Ramsey apparatus
for pseudomagnetic precession with a cold polarised neutron beam at PSI. A
polarised target containing both deuterons and protons will permit a
measurement relative to the incoherent np scattering length, which is know
experimentally with an accuracy of 2.4\times 10^{-4}.

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The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-alg
2
The categories of this paper are: math
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
35
The categories of this paper are: mtrl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: econ
0
The categories of this paper are: hep-ph