J/Ψ photo-production at large z in soft collinear effective theory

One of the outstanding problems in J/{psi} physics is a systematic understanding of the differential photo-production cross section d{sigma}/dz({gamma} + p {yields} J/{psi} + X), where z = E{sub {psi}}/E{sub {gamma}} in the proton rest frame. The theoretical prediction based on the non-relativistic QCD (NRQCD) factorization formalism has a color-octet contribution which grows rapidly in the endpoint region, z {yields} 1, spoiling perturbation theory. In addition there are subleading operators which are enhanced by powers of 1/(1-z) and they must be resumed to all orders. Here an update of a systematic analysis is presented. The approach used to organize the endpoint behavior of the photo-production 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.