Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of the annihilation decay mode $B^{0}\to K^{+}K^{-}$   A search for the $B^{0}\to K^{+}K^{-}$ decay is performed using
$pp$-collision data collected by LHCb. The data set corresponds to integrated
luminosities of 1 and 2 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV,
respectively. This decay is observed for the first time, with a significance of
more than five standard deviations. The analysis also results in an improved
measurement of the branching fraction for the $B_s^0\to \pi^+\pi^-$ decay. The
measured branching fractions are $BR(B^0\to K^+K^-) = (7.80 \pm 1.27 \pm 0.81
\pm 0.21) \times 10^{-8}$ and $BR(B_s^0\to\pi^+\pi^-) = (6.91 \pm 0.54 \pm 0.63
\pm 0.19 \pm 0.40) \times 10^{-7}$. The first uncertainty is statistical, the
second is systematic, the third is due to the uncertainty on the $B^0\to
K^+\pi^-$ branching fraction used as a normalization. For the $B_s^0$ mode, the
fourth accounts for the uncertainty on the ratio of the probabilities for $b$
quarks to hadronize into $B_s^0$ and $B^0$ mesons.

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The categories of this paper are: hep-ph
29
The categories of this paper are: funct-an
32
The categories of this paper are: atom-ph
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
3
The categories of this paper are: physics
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
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The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
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The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
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The categories of this paper are: stat
23
The categories of this paper are: solv-int