Ordered analysis of heavy flavor production in deep-inelastic scattering

At low Q², charm production in deep-inelastic scattering is adequately described by assuming generation in electroweak boson-light parton scattering (dominantly boson-gluon fusion), which naturally incorporates the correct threshold behavior. At high Q² this description is inadequate, since it does not sum logs in Q²/mc², and is replaced by the treatment of the charm quark as a light parton. We show how the problem of going from one description to the other can be solved in a satisfactory manner to all orders. The key ingredient is the constraint of matching the evolution of the physical structure function F₂ order by order in αₛ(Q²), in addition, to the matching of the value of F₂ itself. This leads to new expressions for the coefficient functions associated with the charm parton, which are unique in incorporating both the correct threshold and asymptotic behaviors at each order in perturbation theory. The use of these improved coefficients leads to an improvement in global fits and an excellent description of the observed F2,charm.