PQCD Formulations with Heavy Quark Masses and Global Analysis

TL;DR

This paper reviews heavy quark mass effects in deep inelastic scattering and analyzes various formulations of the general mass variable flavor number scheme, highlighting differences, flaws, and practical implications for global parton distribution analyses.

Contribution

It provides a comprehensive review of GM VFNS formulations, clarifies implementation choices, and discusses improvements over the zero mass scheme.

Findings

Comparison of CTEQ and MSTW schemes

Identification of flaws in ZM VFNS

Discussion on intrinsic heavy flavors

Abstract

We critically review heavy quark mass effects in DIS and their impact on global analyses. We lay out all elements of a properly defined general mass variable flavor number scheme (GM VFNS) that are shared by all modern formulations of the problem. We then explain the freedom in choosing specific implementations and spell out, in particular, the current formulations of the CTEQ and MSTW groups. We clarify the approximations in the still widely-used zero mass variable flavor scheme (ZM VFNS), mention the inherent flaws in its conventional implementation, and consider the possibility of mending some of these flaws. We discuss practical issues concerning the use of parton distributions in various physical applications, in view of the different schemes. And we comment on the possible presence of intrinsic heavy flavors.