Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of Exclusive $B \to X_u \ell \nu$ Decays with $D^{(*)} \ell
  \nu$ Decay Tagging   We report a measurement of the charmless semileptonic decays $B^0 \to \pi^- /
\rho^- \ell^{+} \nu$ and $B^+ \to \pi^0 / \rho^0 \ell^{+} \nu$, based on 253
fb$^{-1}$ of data collected with the Belle detector at the KEKB $e^+e^-$
asymmetric collider. In this analysis, the accompanying $B$ meson is
reconstructed in the semileptonic mode $B \to D^{(*)} \ell \nu$, enabling
detection of the signal modes with high purity. We measure the branching
fractions ${\cal B}(B^0 \to \pi^- \ell^+ \nu) = (1.48\pm 0.20\pm 0.16\pm 0.04)
\times 10^{-4}$, ${\cal B}(B^0 \to \rho^- \ell^+ \nu) = (2.07\pm 0.47\pm
0.25\pm 0.14) \times 10^{-4}$, ${\cal B}(B^+ \to \pi^0 \ell^+ \nu) = (0.76\pm
0.13\pm 0.08\pm 0.04) \times 10^{-4}$ and ${\cal B}(B^+ \to \rho^0 \ell^+ \nu)
= (1.39\pm 0.23\pm 0.17\pm 0.03) \times 10^{-4}$, where the errors are
statistical, experimental systematic, and systematic due to form-factor
uncertainties, respectively. For each mode we also present the partial
branching fractions in three $q^2$ intervals; $q^2 < 8$, $8 \leq q^2 < 16$, and
$q^2 \geq 16$ GeV$^2/c^2$. Based on these results, the magnitude of the
Cabibbo-Kobayashi-Maskawa matrix element $V_{ub}$ is extracted. All of the
presented results are preliminary.

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The categories of this paper are: hep-th
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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
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-fin
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: supr-con
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: q-bio
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The categories of this paper are: physics
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The categories of this paper are: eess