Evolution program for parton densities with perturbative heavy flavor boundary conditions Original Research Article

A new code for the scale evolution of modified-minimal-subtraction-scheme parton densities is described. Through next-to-leading order the program uses exact evolution kernels. In next-to-next-to-leading order approximate evolution kernels are used. For efficiency the program includes analytical results for the evaluation of the weights required for the integrations over the longitudinal momentum fractions of the partons. It also incorporates the operator matrix elements required for the matching conditions across heavy flavor thresholds in higher order perturbation theory. The more efficient handling of the weights implies that the code is faster than similar evolution codes in all modes of operation. The program is written in the C programming language.