Heavy-quark parton distribution functions and their uncertainties

TL;DR

This paper examines the uncertainties in heavy-quark PDFs within the variable flavor number scheme, highlighting differences between charm and bottom quark uncertainties and assessing their impact on single-top-quark production predictions.

Contribution

It provides a detailed analysis of heavy-quark PDF uncertainties and evaluates their effects on collider process predictions, improving upon the common approximation that treats charm and bottom uncertainties equally.

Findings

Charm-quark PDF uncertainties are larger than bottom-quark uncertainties.

Assuming equal uncertainties for charm and bottom quarks is a reasonable first approximation.

Predicted single-top-quark production cross section at Tevatron is 2.12 pb with uncertainties.

Abstract

We investigate the uncertainties of the heavy-quark parton distribution functions in the variable flavor number scheme. Because the charm- and bottom-quark parton distribution functions (PDFs) are constructed predominantly from the gluon PDF, it is a common practice to assume that the heavy-quark and gluon uncertainties are the same. We show that this approximation is a reasonable first guess, but it is better for bottom quarks than charm quarks. We calculate the PDF uncertainty for t-channel single-top-quark production using the Hessian matrix method, and predict a cross section of 2.12+0.32-0.29 pb at run II of the Tevatron.