A Complete Leading-Order, Renormalization-Scheme-Consistent Calculation of Structure Functions

Abstract

We present consistently ordered calculations of the structure functions F_2(x,Q^2) and F_L(x,Q^2), in different expansion schemes. After discussing the standard expansion in powers of alpha_s(Q^2) we consider a leading-order expansion in ln(1/x) and finally an expansion which is leading order in both ln(1/x) and alpha_s(Q^2), and which is the only really correct expansion scheme. Ordering the calculation in a renormalization-scheme-consistent manner, there is no factorization scheme dependence, and the calculational method naturally includes to the ``physical anomalous dimensions'' of Catani. However, it imposes stronger constraints than just the use of these effective anomalous dimensions. A relationship between the small-x forms of the inputs F_2(x,Q_I^2) and F_L(x,Q_I^2) is predicted. Analysis of a wide range of data for F_2(x,Q^2) is performed, and a very good global fit obtained, particularly for data at small x. The fit allows a prediction for F_L(x,Q^2) to be produced, which is smaller than those produced by the usual NLO-in-alpha_s(Q^2) fits to F_2(x,Q^2) and different in shape.