Abstract
Recent observations of the $J/\ensuremath{\psi}$ spectrum produced in ${e}^{+}{e}^{\ensuremath{-}}$ collisions at the $\ensuremath{\Upsilon}(4S)$ resonance are in conflict with fixed-order calculations using the nonrelativsitic QCD effective theory (NRQCD). One problem is an enhancement in the cross section when the $J/\ensuremath{\psi}$ has maximal energy, due to large perturbative corrections (Sudakov logarithms). In a recent paper, the Sudakov logarithms in the color-octet contribution were summed by combining NRQCD with the soft-collinear effective theory. However, to be consistent, the color-singlet contributions must also be summed in the endpoint region which was not done in that paper. In this paper, we sum the leading logarithms in the color-singlet contribution to the $J/\ensuremath{\psi}$ production cross section. We find that the color-singlet cross section is suppressed near the endpoint compared to the fixed-order NRQCD prediction.
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