Problems of Double Charm Production in $e^+e^-$ Annihilation at $sqrt{s}=10.6$ GeV.pdfVIP

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Problems of Double Charm Production in $e^+e^-$ Annihilation at $sqrt{s}=10.6$ GeV.pdf

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ProblemsofDoubleCharmProductionin$e^e^-$Annihilationat$sqrt{s}=10.6$GeV

a r X i v : h e p - p h / 0 2 1 1 1 8 1 v 4 2 0 M a r 2 0 0 3 Problems of Double-Charm Production in e+e? Annihilation at √ s = 10.6 GeV Kui-Yong Liu (a) Zhi-Guo He (a) and Kuang-Ta Chao (b,a) (a) Department of Physics, Peking University, Beijing 100871, People’s Republic of China (b) China Center of Advanced Science and Technology (World Laboratory), Beijing 100080, People’s Republic of China Abstract Using the nonrelativistic QCD(NRQCD) factorization formalism, we calculate the color-singlet cross sections for exclusive production processes e+ + e? → J/ψ + ηc and e+ + e? → J/ψ + χcJ (J = 0, 1, 2) at the center-of-mass energy √ s=10.6 GeV. The cross sections are estimated to be 5.5fb, 6.7fb, 1.1fb, and 1.6fb for ηc, χc0, χc1 and χc2, respectively. The calculated J/ψ + ηc production rate is smaller than the recent Belle data by about an order of magnitude, which might indicate the failure of perturbative QCD calculation to explain the double-charmonium production data. The complete O(α2s) color-singlet cross section for e+ + e? → χc0 + cc? is calculated. In addition, we also evaluate the ratio of exclusive to inclusive production cross sections. The ratio of J/ψηc production to J/ψcc? production could be consistent with the experimental data. PACS number(s): 12.40.Nn, 13.85.Ni, 14.40.Gx Heavy quarkonium production is interesting in understanding both perturbative and non- perturbative quantum chromodynamics (QCD). In recent years the charmonium production has been studied in various processes, such as in hadron-hadron collision, electron-proton collision, fixed target experiments, B meson decays, as well as Z0 decays. Among them, the study of charmonium production in e+e? annihilation is particularly interesting in testing the quarkonium production mechanisms, the color-singlet model and the color-octet model in the nonrelativistic QCD (NRQCD)[1] approach. This is not only because of the simpler parton structure involved in this process, which may be helpful in