J/Ψ photo-production at large z in soft collinear effective theory
One of the outstanding problems in J/Ψ physics is a systematic understanding of the differential photo-production cross section dσ/dz(γ+p → J/Ψ + X), where z = EΨ,/E gamma;/ in the proton rest frame. The theoretical prediction based on the nonrelativistic QCD (NRQCD) factorization formalism has a color-octet contribution which grows rapidly in the endpoint region, z -→ 1, spoiling perturbation theory. In addition there are subleading operators which are enhanced by powers of 1/(1 - z) and they must be resummed to all orders. Here an update of a systematic analysis is presented. The approach used to organize the endpoint behavior of the photoproduction cross section is based on a combination of NRQCD and soft collinear effective theory. While a final result is not yet available, an intermediate result indicates that better agreement between theory and data will be achieved in this framework. Copyright © 2006 by World Scientific Publishing Co. Pte. Ltd.
Fleming, S; Leibovich, AK; Mehen, T
Proceedings of the Ringberg Workshop on New Trends in Hera Physics 2005
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