Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A new part-per-million measurement of the positive muon lifetime and
  determination of the Fermi Constant   The Fermi Constant, G_F, describes the strength of the weak force and is
determined most precisely from the mean life of the positive muon, tau_mu.
Advances in theory have reduced the theoretical uncertainty on G_F as
calculated from tau_mu to a few tenths of a part per million (ppm). Until
recently, the remaining uncertainty on G_F was entirely experimental and
dominated by the uncertainty on tau_mu. We report the MuLan collaboration's
recent 1.0 ppm measurement of the positive muon lifetime. This measurement is
over a factor of 15 more precise than any previous measurement, and is the most
precise particle lifetime ever measured. The experiment used a time-structured
low-energy muon beam and an array of plastic scintillators read-out by waveform
digitizers and a fast data acquisition system to record over 2 times 10^{12}
muon decays. Two different in-vacuum muon-stopping targets were used in
separate data-taking periods. The results from these two data-taking periods
are in excellent agreement. The combined results give
tau_{mu^+}({MuLan})=2196980.3(2.2) ps. This measurement of the muon lifetime
gives the most precise value for the Fermi Constant: G_F({MuLan}) = 1.1663788
(7) \times 10^{-5} {GeV}^{-2} (0.6 ppm). The lifetime is also used to extract
the mu^-p singlet capture rate, which determines the proton's weak induced
pseudoscalar coupling g_P.

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The categories of this paper are: mtrl-th
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The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: cmp-lg
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The categories of this paper are: dg-ga
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The categories of this paper are: math
1
The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: physics
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org