We investigate the origin of the double logarithms of Q2/m c2 that appear in the calculation of the cross section for e+e- → J/π +ηc at next-to-leading order in the strong coupling αs. Here, Q2 is the square of the center-of-momentum energy, and mc is the charm-quark mass. We find that, diagram-by-diagram, the double logarithms are accounted for by Sudakov double logarithms and endpoint double logarithms. The Sudakov double logarithms cancel in the sum over all diagrams, but the endpoint double logarithms do not. We reinterpret the endpoint double logarithms in terms of a leading region of loop integration in which a spectator fermion line becomes soft and collinear. This reinterpretation may simplify the process of establishing an all-orders factorization theorem for this helicity-flip process, which, in turn, might allow one to resum logarithms of Q2/mc2 to all orders in αs. Copyright owned by the author(s).
|Proceedings of Science
|Published - 2012
|10th Conference on Quark Confinement and the Hadron Spectrum, Confinement 2012 - Munich, Germany
Duration: 2012 Oct 8 → 2012 Oct 12
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