Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurements of the Mass, total Width and Two-Photon Partila Width of
  the $\eta_{c}$ Meson   Using 13.4 $fb^{-1}$ of data collected with the CLEO detector at the Cornell
Electron Storage Ring, we have observed 300 events for the two-photon
production of ground-state pseudo-scalar charmonium in the decay $\eta_c$ ->
$K_S K^{\mp} \pi^{\pm}$. We have measured the $\eta_c$ mass to be (2980.4 +-
2.3 (stat) +- 0.6 (sys)) MeV and its full width as (27.0 +- 5.8 (stat) +- 1.4
(sys)) MeV. We have determined the two-photon partial width of the $\eta_c$
meson to be (7.6 +- 0.8 (stat) +- 0.4 (sys) +- 2.3 (br)) keV, with the last
uncertainty associated with the decay branching fraction.

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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: atom-ph
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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: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: funct-an