Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Study of $\pi^0$ pair production in single-tag two-photon collisions   We report a measurement of the differential cross section of $\pi^0$ pair
production in single-tag two-photon collisions, $\gamma^* \gamma \to \pi^0
\pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to
30 GeV$^2$, where $Q^2$ is the negative of the invariant mass squared of the
tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and $|\cos
\theta^*|$ < 1.0 for the total energy and pion scattering angle, respectively,
in the $\gamma^* \gamma$ center-of-mass system. The results are based on a data
sample of 759 fb$^{-1}$ collected with the Belle detector at the KEKB
asymmetric-energy $e^+ e^-$ collider. The transition form factor of the
$f_0(980)$ and that of the $f_2(1270)$ with the helicity-0, -1, and -2
components separately are measured for the first time and are compared with
theoretical calculations.

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The categories of this paper are: physics
9
The categories of this paper are: nlin
2
The categories of this paper are: math
34
The categories of this paper are: chem-ph
35
The categories of this paper are: mtrl-th
36
The categories of this paper are: cmp-lg
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The categories of this paper are: nucl-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: supr-con
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The categories of this paper are: plasm-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: stat