Update of MRST partons

TL;DR

MRST provides an updated set of parton distributions with new variations to quantify uncertainties in $W$ and $Z$ production cross sections at the Tevatron and LHC, and compares results with CTEQ5. The analysis covers light, heavy, and gluon distributions, detailing how deuterium corrections, heavy-flavor schemes, and intrinsic $k_T$ affect predictions, and explains discrepancies with CTEQ5. It uses the Thorne-Roberts matching prescription for heavy flavors and explores large- and small-$x$ gluon constraints, showing that cross-section predictions are sensitive to these details. A corrected evolution bug in MRST modestly raises predicted $W$ cross sections and reduces discrepancies with CTEQ5, yet NNLO analyses and robust uncertainty quantification remain essential for precise collider predictions.

Abstract

We discuss topical issues concerning the MRST parton analysis. We introduce some new parton sets in order to estimate the uncertainty in the cross sections predicted for W and Z production at the Tevatron and the LHC. We compare with CTEQ5 partons.

Figures (1)

• Figure 1: NNLO NV predictions of the $W$ production cross section at the Tevatron from seven different sets of NLO MRST partons, and from CTEQ5HQ partons. Also shown are the cross sections measured by the CDF and D0 collaborations.