Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the branching fraction for $B^{0} \rightarrow \pi^{0}
  \pi^{0}$ decays reconstructed in 2019-2020 Belle II data   We report the first reconstruction of the $B^{0} \to \pi^{0} \pi^{0}$ decay
mode at Belle II using samples of 2019 and 2020 data that correspond to 62.8
fb$^{-1}$ of integrated luminosity. We find $14.0^{+6.8}_{-5.6}$ signal decays,
corresponding to a significance of 3.4 standard deviations and determine a
branching ratio of $\mathcal{B}(B^{0} \rightarrow \pi^{0} \pi^{0}) =
[0.98^{+0.48}_{-0.39} \pm 0.27] \times 10^{-6}$. The results agree with
previous determinations and contribute important information to an early
assessment of detector performance and Belle II's potential for future
determinations of $\alpha/\phi_2$ using $B \rightarrow \pi \pi$ modes.

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The categories of this paper are: eess
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The categories of this paper are: dg-ga
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The categories of this paper are: funct-an
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The categories of this paper are: hep-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: econ
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The categories of this paper are: adap-org
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The categories of this paper are: astro-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: stat
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg