Precision measurement and interpretation of inclusive $$W^+$$ W + , $$W^-$$ W -

Abstract

High-precision measurements by the ATLAS Collaboration are presented of inclusive , and () Drell–Yan production cross sections at the LHC. The data were collected in proton–proton collisions at with an integrated luminosity of . Differential and cross sections are measured in a lepton pseudorapidity range . Differential cross sections are measured as a function of the absolute dilepton rapidity, for , for three intervals of dilepton mass, , extending from 46 to . The integrated and differential electron- and muon-channel cross sections are combined and compared to theoretical predictions using recent sets of parton distribution functions. The data, together with the final inclusive scattering cross-section data from H1 and ZEUS, are interpreted in a next-to-next-to-leading-order QCD analysis, and a new set of parton distribution functions, ATLAS-epWZ16, is obtained. The ratio of strange-to-light sea-quark densities in the proton is determined more accurately than in previous determinations based on collider data only, and is established to be close to unity in the sensitivity range of the data. A new measurement of the CKM matrix element is also provided.

QCD analysis of the ATLAS and CMS W± and Z cross-section measurements and implications for the strange sea density

“…The high precision measurements of the inclusive W and Z boson cross section at the LHC recently performed by the ATLAS Collaboration provide new constraints on the strange quark density in the low-x regime [8] and a corresponding set of NNLO PDFs, the ATLASepWZ16 PDFs. Specifically, the data support the hypothesis of a symmetric composition of the light quark sea at low-x for both high and low scales.…”

Constraints on the Parton Density Functions of the Proton by Measurements with the ATLAS Detector

“…CT [18] sets, a reduction in the size of the uncertainty of the strange density is observed together with an increase from the values from the original fits, to around unity [13].…”

“…The ATLAS Collaboration have also recently published data for Electroweak boson production with a precision analysis of inclusive W and Z production from the 2011 data, with the precise measurment of the Z cross section both near the Z pole, and in the low and high mass regions [13]. The NNLO corrections to these cross sections have been known for some time.…”

“…With the newer data [13], existing PDF sets can be profiled to determine which is the most consistent with the data and evaluate the approximate changes that might be expected to the sets if they had been performed including these data. Following this procedure for the MMHT [6] and…”

“…Figure 3: The u and d valence quark distributions, and the ratio of the strange quark density from the ATLAS epWZ16 QCD fit [13].…”