Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Measurement of the Mass Difference m(B0) - m(B+)   Using 230 million B Bbar events recorded with the BABAR detector at the e+ e-
storage rings PEP-II, we reconstruct approximately 4100 B0 to J/psi K+ pi- and
9930 B+ to J/psi K+ decays with J/psi to mu+ mu- and e+ e-. From the measured
B-momentum distributions in the e+ e- rest frame, we determine the mass
difference m(B0) - m(B+) = (+0.33 +- 0.05 +- 0.03) MeV/c^2.

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The categories of this paper are: ao-sci
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The categories of this paper are: plasm-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: stat
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: hep-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: patt-sol
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: quant-ph