The Effect of Variable Flavour Number Scheme Variations on PDFs and Cross Sections

Understand

I consider variations in the definition of a General-Mass Variable Flavour Number Scheme (GM-VFNS) for heavy flavour structure functions, both at next-to-leading order (NLO) and at next-to-next-to leading order (NNLO).

• I also define a new "optimal" scheme choice improving the smoothness of the transition from one flavour number to the next.
• At both NLO and NNLO I investigate the variation of the structure function for a fixed set of parton distribution functions (PDFs) and also the change in the distributions when a new MSTW-type global fit to data is performed for each GM-VFNS.
• At NLO the parton distributions, and predictions using them at hadron colliders, can vary by ~2% from the mean value.