Pinning down the large-x gluon with NNLO top-quark pair differential distributions

TL;DR

This paper demonstrates that differential distributions from top-quark pair production at the LHC provide significant constraints on the large-x gluon PDF, comparable to inclusive jet data, and are crucial for future global PDF fits.

Contribution

It introduces the first NNLO analysis of top-quark pair differential distributions' impact on the large-x gluon PDF within the NNPDF framework.

Findings

Differential distributions significantly constrain the large-x gluon.

Constraints are comparable to those from inclusive jet data.

Data from ATLAS and CMS are compatible and complementary.

Abstract

Top-quark pair production at the LHC is directly sensitive to the gluon PDF at large x. While total cross-section data is already included in several PDF determinations, differential distributions are not, because the corresponding NNLO calculations have become available only recently. In this work we study the impact on the large-x gluon of top-quark pair differential distributions measured by ATLAS and CMS at $\sqrt{s}=8$ TeV. Our analysis, performed in the NNPDF3.0 framework at NNLO accuracy, allows us to identify the optimal combination of LHC top-quark pair measurements that maximize the constraints on the gluon, as well as to assess the compatibility between ATLAS and CMS data. We find that differential distributions from top-quark pair production provide significant constraints on the large-x gluon, comparable to those obtained from inclusive jet production data, and thus should become an important ingredient for the next generation of global PDF fits.