Constraining the top-quark mass within the global MSHT PDF fit

TL;DR

This paper demonstrates that incorporating top-quark pair production data into the MSHT global PDF fit significantly constrains the top-quark mass and provides limited bounds on the strong coupling, resulting in a precise mass measurement consistent with world averages.

Contribution

The study introduces a method to constrain the top-quark mass and strong coupling within a global PDF fit using differential and total cross section data from collider experiments.

Findings

Top-quark mass determined as 173.0 ± 0.6 GeV.

Constraints on the strong coupling are limited but present.

High-x gluon PDF shows changes within uncertainties.

Abstract

We examine the ability of experimental measurements of top-quark pair production to constrain both the top-quark mass and the strong coupling within the global MSHT parton distribution function (PDF) fit. Specifically, we consider ATLAS and CMS measurements of differential distributions taken at a centre-of-mass energy of 8 TeV, as well as $t\bar{t}$ total cross section data taken at a variety of experiments, and compare to theoretical predictions including next-to-next-to-leading order corrections. We find that supplementing the global fit with this additional information results in relatively strong constraints on the top-quark mass, and is also able to bound the strong coupling in a limited fashion. Our final result is $m_t=173.0\pm0.6~\mathrm{GeV}$ and is compatible with the world average pole mass extracted from cross section measurements of $172.5\pm0.7~\mathrm{GeV}$ by the Particle Data Group. We also study the effect of different top-quark masses on the gluon parton distribution function, finding changes at high $x$ which nonetheless lie within the large PDF uncertainties in this region.