The t-tbar cross-section at 1.8 and 1.96 TeV: a study of the systematics due to parton densities and scale dependence
M. Cacciari, S. Frixione, M. L. Mangano, P. Nason, G. Ridolfi
TL;DR
This work addresses the precision prediction of the top-quark pair production cross-section at Tevatron energies by combining full NLO QCD matrix elements with all-order soft-gluon resummation (NLL) and incorporating PDFs with quantified uncertainties. The authors systematically assess two main sources of theoretical uncertainty: renormalization/factorization scale variations and parton distribution function (PDF) uncertainties, using CTEQ6 and MRST error sets and additional alpha_s variations. They find that NLL resummation reduces scale uncertainty from about 10% at NLO to roughly 5%, while PDF uncertainties propagate through eigenvector variations to produce comparable bands, with results tabulated across energies, top masses, and scale choices. The study provides central values with explicit uncertainty estimates, enabling more reliable comparisons with experimental measurements and highlighting the importance of PDF uncertainty in precision cross-section predictions.
Abstract
We update the theoretical predictions for the t-tbar production cross-section at the Tevatron, taking into account the most recent determinations of systematic uncertainties in the extraction of the proton parton densities.