Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Resonances and weak interactions in $D^+ \to\pi^+ \pi^- \pi^+$ decays   We describe the $\pi\pi$ $S$-wave in $D^+ \to\pi^+ \pi^- \pi^+$ decays using
a unitary model for the $\pi\pi$ Final State Interactions (FSI). The three body
decay is treated as a quasi two-body process where, at the weak vertex, the D
meson decays into a resonance and a pion. The weak part of the decay amplitude
is evaluated using the effective weak Hamiltonian within the factorization
approximation.

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The categories of this paper are: hep-th
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The categories of this paper are: hep-lat
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The categories of this paper are: math
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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: solv-int
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The categories of this paper are: mtrl-th
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
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The categories of this paper are: patt-sol
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph