Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Nab: Measurement Principles, Apparatus and Uncertainties   The Nab collaboration will perform a precise measurement of 'a', the
electron-neutrino correlation parameter, and 'b', the Fierz interference term
in neutron beta decay, in the Fundamental Neutron Physics Beamline at the SNS,
using a novel electric/magnetic field spectrometer and detector design. The
experiment is aiming at the 10^{-3} accuracy level in (Delta a)/a, and will
provide an independent measurement of lambda = G_A/G_V, the ratio of
axial-vector to vector coupling constants of the nucleon. Nab also plans to
perform the first ever measurement of 'b' in neutron decay, which will provide
an independent limit on the tensor weak coupling.

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The categories of this paper are: astro-ph
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The categories of this paper are: patt-sol
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
18
The categories of this paper are: econ
24
The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
21
The categories of this paper are: adap-org
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
32
The categories of this paper are: atom-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph