The impact of PDF and alphas uncertainties on Higgs Production in gluon fusion at hadron colliders

TL;DR

This paper systematically evaluates the uncertainties in Higgs production cross sections due to PDFs and alpha_s at colliders, comparing different PDF sets and proposing a conservative uncertainty estimate.

Contribution

It provides a detailed comparison of PDF and alpha_s uncertainties across multiple PDF sets and introduces a simple method to estimate combined uncertainties conservatively.

Findings

PDF set results are consistent with a common alpha_s value.

Quadrature addition of PDF and alpha_s uncertainties is effective.

Estimated total uncertainties are about 10% at Tevatron and 5% at LHC.

Abstract

We present a systematic study of uncertainties due to parton distributions and the strong coupling on the gluon-fusion production cross section of the Standard Model Higgs at the Tevatron and LHC colliders. We compare procedures and results when three recent sets of PDFs are used, CTEQ6.6, MSTW08 and NNPDF1.2, and we discuss specifically the way PDF and strong coupling uncertainties are combined. We find that results obtained from different PDF sets are in reasonable agreement if a common value of the strong coupling is adopted. We show that the addition in quadrature of PDF and alphas uncertainties provides an adequate approximation to the full result with exact error propagation. We discuss a simple recipe to determine a conservative PDF+alphas uncertainty from available global parton sets, and we use it to estimate this uncertainty on the given process to be about 10% at the Tevatron and 5% at the LHC for a light Higgs.