Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Searches for the decays B0 -> l+ tau- and B+ -> l+ nu (l=e,mu) using
  hadronic tag reconstruction   We present searches for the leptonic decays B+ -> l+ nu and the lepton flavor
violating decays B0 -> l+ tau-, where l=e,mu, with data collected by the BaBar
experiment at SLAC. This search demonstrates a novel technique in which we
fully reconstruct the accompanying Bbar in Upsilon(4S)->BBbar events, and look
for a monoenergetic lepton from the signal B decay. The signal yield is
extracted from a fit to the signal lepton candidate momentum distribution in
the signal B rest frame. Using a data sample of approximately 378 million BBbar
pairs (342fb-1), we find no evidence of signal in any of the decay modes.
Branching fraction upper limits of B(B+ -> e+ nu)<5.2x10^-6, B(B+ -> mu+
nu)<5.6x10^-6, B(B0 -> e+ tau-)<2.8x10^-5 and B(B0 -> mu+ tau-)<2.2x10^-5, are
obtained at 90% confidence level.

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The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
35
The categories of this paper are: mtrl-th
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The categories of this paper are: q-fin
1
The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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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: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: stat
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The categories of this paper are: hep-th