The impact of PDF uncertainties on the measurement of the W boson mass at the Tevatron and the LHC

TL;DR

This study quantitatively assesses how uncertainties in proton PDFs, alpha_S, and charm mass affect the precision of W boson mass measurements at hadron colliders, concluding that current PDF uncertainties are below 10 MeV and do not hinder 10 MeV accuracy goals.

Contribution

It provides a detailed analysis of PDF-related uncertainties on W mass measurements at the Tevatron and LHC using multiple PDF sets and NLO-QCD calculations.

Findings

PDF uncertainties are below 10 MeV for W mass measurements.

Current PDF uncertainties do not prevent achieving 10 MeV measurement precision.

The analysis covers different collider energies and uses multiple event generators.

Abstract

We study at a quantitative level the impact of the uncertainties on the value of the W boson mass measured at hadron colliders due to: the proton parton distribution functions (PDFs), the value of the strong coupling constant alpha_S and the value of the charm mass used in the PDF determination. The value of the W boson mass is extracted, by means of a template fit technique, from the lepton-pair transverse mass distribution measured in the charged current Drell-Yan process. We study the determination of M_W at the Tevatron and at the LHC with 7 and 14 TeV of center-of-mass energy in a realistic experimental setup. The analysis has been done at the Born level using the event generator HORACE and at NLO-QCD using the event generators DYNNLO and ResBos. We consider the three global PDF sets, CTEQ6.6, MSTW2008 and NNPDF2.1. We estimate that the total PDF uncertainty on M_W is below 10 MeV both at the Tevatron and at the LHC for all energies and final states. We conclude that PDF uncertainties do not challenge a measurement of the W boson mass at the level of 10 MeV accuracy.