Resummation of Large Endpoint Corrections to Color-Octet J/psi Photoproduction
Author | : |
Publisher | : |
Total Pages | : |
Release | : 2006 |
ISBN-10 | : OCLC:871263090 |
ISBN-13 | : |
Rating | : 4/5 (90 Downloads) |
Book excerpt: An unresolved problem in J/[psi] phenomenology is a systematic understanding of the differential photoproduction cross section, d[sigma]/dz [[gamma] + p → J/[psi] + X], where z = E{sub [psi]}/E{sub {gamma}} in the proton rest frame. In the non-relativistic QCD (NRQCD) factorization formalism, fixed-order perturbative calculations of color-octet mechanisms suffer from large perturbative and nonperturbative corrections that grow rapidly in the endpoint region, z → 1. In this paper, NRQCD and soft collinear effective theory are combined to resum these large corrections to the color-octet photoproduction cross section. We derive a factorization theorem for the endpoint differential cross section involving the parton distribution function and the color-octet J/{psi} shape functions. A one loop matching calculation explicitly confirms our factorization theorem at next-to-leading order. Large perturbative corrections are resummed using the renormalization group. The calculation of the color-octet contribution to d[sigma]/dz is in qualitative agreement with data. Quantitative tests of the universality of color-octet matrix elements require improved knowledge of shape functions entering these calculations as well as resummation of the color-singlet contribution which accounts for much of the total cross section and also peaks near the endpoint.