A Measurement of the ψ‧ to J/ψ production ratio in 920 GeV proton-nucleus interactions
Abstract
Ratios of the ψ‧ over the J/ψ 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 ψ‧ and J/ψ states were reconstructed in both the μ+μ- and the e+e- decay modes. The measurements covered the kinematic range -0.35≤xF≤0.1 with transverse momentum pT≤4.5 GeV/c. The angular dependence of the ratio has been used to measure the difference of the ψ‧ and J/ψ polarization. All results for the muon and electron decay channels are in good agreement: their ratio, averaged over all events, is Rψ‧(μ)/Rψ‧(e)=1.00±0.08±0.04. This result constitutes a new, direct experimental constraint on the double ratio of branching fractions, (B‧(μ)B(e))/(B(μ)B‧(e)), of ψ‧ and J/ψ in the two channels. The ψ‧ to J/ψ production ratio is almost constant in the covered xF range and shows a slow increase with pT.
- Publication:
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European Physical Journal C
- Pub Date:
- January 2007
- DOI:
- 10.1140/epjc/s10052-006-0139-9
- arXiv:
- arXiv:hep-ex/0607046
- Bibcode:
- 2007EPJC...49..545A
- Keywords:
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- High Energy Physics - Experiment
- E-Print:
- 20 pages, 9 figures