Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of the Decay $B^{0} \to \pi^{0}\pi^{0}$   We present an observation of the decay $B^{0} \to \pi^{0} \pi^{0}$ based on a
sample of 124 million $B\bar{B}$ pairs recorded by the BABAR detector at the
PEP-II asymmetric-energy $B$ Factory at SLAC. We observe $46 \pm 13 \pm 3$
events, where the first error is statistical and the second is systematic,
corresponding to a significance of 4.2 standard deviations including systematic
uncertainties. We measure the branching fraction $\BR(B^{0} \to \pi^{0}
\pi^{0}) = (2.1 \pm 0.6 \pm 0.3) \times 10^{-6}$, averaged over $B^{0}$ and
$\bar{B}^{0}$ decays.

25
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: acc-phys
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The categories of this paper are: astro-ph
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
12
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: mtrl-th
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The categories of this paper are: gr-qc
3
The categories of this paper are: physics
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The categories of this paper are: funct-an
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The categories of this paper are: dg-ga
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The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an