Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Measurement of the Psi' to J/psi Production Ratio in 920 GeV
  Proton-Nucleus Interactions   Ratios of the Psi' over the J/psi production cross sections in the dilepton
channel for C, Ti and W targets have been measured in 920 GeV proton-nucleus
interactions with the HERA-B detector at the HERA storage ring. The Psi' and
J/psi states were reconstructed in both the mu+mu- and the e+e- decay modes.
The measurements covered the kinematic range -0.35 < x_F < 0.1 with transverse
momentum p_T < 4.5 GeV/c. The Psi' to J/psi production ratio is almost constant
in the covered x_F range and shows a slow increase with p_T. The angular
dependence of the ratio has been used to measure the difference of the Psi' and
J/psi polarization. All results for the muon and electron decay channels are in
good agreement: their ratio, averaged over all events, is
R_psi'(mu)/R_psi'(e)=1.00+-0.08+-0.04. This result constitutes a new, direct
experimental constraint on the double ratio of branching fractions,
(B'(mu)*B(e))/(B(mu)*B'(e)), of Psi' and J/psi in the two channels.

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The categories of this paper are: quant-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: alg-geom
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The categories of this paper are: funct-an
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: chem-ph
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The categories of this paper are: stat
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The categories of this paper are: hep-ph
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The categories of this paper are: nlin
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: q-bio
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The categories of this paper are: solv-int