paper

Determination of color-octet matrix elements from e^+e- process at low energies

arXiv:hep-ph/9701361 · doi:10.1103/PhysRevD.56.1663

Abstract

We present an analysis of the preliminary experimental data of direct j/psi production in e^e- process at low energies. We find that the color-octet contributions are crucially important to the cross section at this energy region, and their inclusion produces a good description of the data. By fitting to the data, we extract the individual values of two color-octet matrix elements: <{\cal O}_8^ψ(^1S_0)> \approx 1.1\times 10^{-2} GeV^3, <{\cal O}_8^ψ(^3P_0)> m_c^2\approx 7.4\times 10^{-3}GeV^3. We discuss the allowed range of the two matrix elements constrained by the theoretical uncertainties. We find that <{\cal O}_8^ψ(^1S_0)> is poorly determined because it is sensitive to the variation of the choice of m_c, α_s and <{\cal O}_1^ψ(^3S_1)>. However <{\cal O}_8^ψ(^3P_0)> m_c^2 is quite stable (about (6-9)\times 10^{-3}GeV^3) when the parameters vary in reasonable ranges. The uncertainties due to large experimental errors are also discussed.

13 page, RevTex, 2 figures in postscript. To appear in Phys. Rev. D

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