Double logarithms in e+e- →j /ψ+ηc

Double logarithms of Q2/mc2 that appear in the cross section for e+e-→J/ψ+ηc at next-to-leading order (NLO) in the strong coupling αs account for the bulk of the NLO correction at B-factory energies. (Here, Q2 is the square of the center-of-momentum energy, and mc is the charm-quark mass.) We analyze the double logarithms that appear in the contribution of each NLO Feynman diagram, and we find that the double logarithms arise from both the Sudakov and the end-point regions of the loop integration. The Sudakov double logarithms cancel in the sum over all diagrams. We show that the end-point region of integration can be interpreted as a pinch-singular region in which a spectator fermion line becomes soft or soft and collinear to a produced meson. This interpretation may be important in establishing factorization theorems for helicity-flip processes, such as e+e-→J/ψ+ηc, and in resumming logarithms of Q2/mc2 to all orders in αs.