Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the I=1/2 $K \pi$ $\mathcal{S}$-wave amplitude from
  Dalitz plot analyses of $\eta_c \to K \bar K \pi$ in two-photon interactions   We study the processes $\gamma \gamma \to K^0_S K^{\pm}\pi^{\mp}$ and $\gamma
\gamma \to K^+ K^- \pi^0$ using a data sample of 519~$fb^{-1}$ recorded with
the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+ e^-$
collider at center-of-mass energies at and near the $\Upsilon(nS)$ ($n =
2,3,4$) resonances. We observe $\eta_c$ decays to both final states and perform
Dalitz plot analyses using a model-independent partial wave analysis technique.
This allows a model-independent measurement of the mass-dependence of the
$I=1/2$ $K \pi$ $\mathcal{S}$-wave amplitude and phase. A comparison between
the present measurement and those from previous experiments indicates similar
behaviour for the phase up to a mass of 1.5 $GeV/c^2$. In contrast, the
amplitudes show very marked differences. The data require the presence of a new
$a_0(1950)$ resonance with parameters $m=1931 \pm 14 \pm 22 \ MeV/c^2$ and
$\Gamma=271 \pm 22 \pm 29 \ MeV$.

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The categories of this paper are: q-bio
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The categories of this paper are: econ
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: stat
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The categories of this paper are: q-alg
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga