Intrinsic charm in a matched general-mass scheme

TL;DR

This paper extends the FONLL scheme to allow for a fitted charm quark distribution, enabling more flexible modeling of heavy quark contributions in deep-inelastic scattering and improving parton distribution function determinations.

Contribution

It introduces a generalized FONLL framework that permits initial parameterization of heavy quark PDFs, enhancing the treatment of intrinsic charm in QCD calculations.

Findings

Fitted charm distributions can significantly impact $F_2^c$ predictions.

The extended scheme allows for more flexible PDF modeling.

Potential improvements in deep-inelastic scattering analyses.

Abstract

The FONLL general-mass variable-flavour number scheme provides a framework for the matching of a calculation in which a heavy quark is treated as a massless parton to one in which the mass dependence is retained throughout. We describe how the usual formulation of FONLL can be extended in such a way that the heavy quark parton distribution functions are freely parameterized at some initial scale, rather than being generated entirely perturbatively. We specifically consider the case of deep-inelastic scattering, in view of applications to PDF determination, and the possible impact of a fitted charm quark distribution on $F_2^c$ is assessed.