We have studied the production of J/ψ and ψ(2S) charmonium mesons in 515 GeV/c π−Be collisions in the Feynman-x range 0.1<xF<0.8. J/ψ mesons were detected via their decay into μ+μ−, and ψ(2S) mesons were studied in both the μ+μ− and J/ψπ+π− decay modes. J/ψ differential cross sections have been measured as functions of xF,pT2, and the cosine of the Gottfried-Jackson decay angle. We measure an inclusive J/ψ cross section of B(J/ψ→μ+μ−)σ(π−Be→J/ψ+X)/A= [9.3±0.1(stat)±1.1(syst)] nb/nucleon for J/ψ xF≳0.1. Our results are compared with those from other experiments performed at lower beam energies. We also measure the differential ψ(2S) cross section as a function of both xF and pT2, and a ψ(2S) inclusive cross section of B(ψ(2S)→J/ψπ+π−)σ(π−Be→ψ(2S)+X)/A=[7. 4±1.5(stat)±1.2(syst)] nb/nucleon for ψ(2S) xF≳0.1. The fraction of the inclusive J/ψ yield due to ψ(2S) meson decays is 0.083±0.017(stat) ±0.013(syst), and the observed ratio of ψ(2S) decay rates is B(ψ(2S)→J/ψπ+π−)/B(ψ(2S)→μ+μ−) =30.2±7.2(stat)±6.8(syst). We have searched for production of ‘‘hidden’’ charm resonances decaying into either J/ψπ±,ψ(2S)π±, or J/ψπ+π− systems, and report an upper limit of 3.1 nb/nucleon for the product of branching ratio and cross section for the recently reported enhancement at a J/ψπ+π− mass of 3.836 GeV/c2. © 1996 The American Physical Society.
We report on the production of J/psi mesons in 530 and 800 GeV/c proton - Be collisions in the Feynman-x range 0.0 < xf < 0.6. The J/psi mesons were detected via decays into opposite sign muon pairs. Differential distributions for J/psi production have been measured as functions of xf, pT^2, and cosine of the Gottfried-Jackson decay angle. These distributions are compared with results on J/psi production obtained in 515 GeV/c pion - Be collisions, measured by the same experiment, as well as with results from other experiments using incident protons.
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Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.
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