CERN Accelerating science

ATLAS Slides
Report number	ATL-PHYS-SLIDE-2024-044
Title	EW and QCD Measurements
Author(s)	Cardoso Silva, Julia Manuela (The University of Edinburgh (GB))
Corporate author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Submitted to	XXXVII Rencontres de Physique de La Vallée d'Aoste, La Thuile, Italy, It, 3 - 9 Mar 2024
Submitted by	[email protected] on 26 Mar 2024
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	EWEAK ; QCD
Abstract	Precise measurements with the ATLAS and CMS experiments at the LHC are used to determine fundamental parameters of the Standard Model, and provide stringent tests of the electroweak theory and perturbative QCD. In this talk, extraordinarily precise double-differential measurement of the Z boson in the full phase space of the decay leptons at a centre-of-mass energy of 8 TeV are discussed. The recoil of the Z-boson is sensitive to quark and gluon emissions and is used to determine the strong coupling constant in a novel approach. Differential measurements of multijet cross-section ratios of two- and three-jet production are discussed and compared to state-of-the-art NLO and NNLO predictions. In addition, ATLAS & CMS have used these events to improve our understanding of jet formation and structure. The measured distributions are compared to a range of hadronisation models and can be used to tune and improve them in the future. The production of electroweak gauge bosons also serves to test predictions of QCD. A range of measurements of vector bosons in association with jets, as well as a search for exclusive hadronic decays of the W boson are highlighted. Measurements of the transverse momentum of the W and Z boson at 5 and 13 TeV from dedicated LHC runs with reduced instantaneous luminosity are also presented, and compared to state-of-the-art predictions of perturbative QCD, supplemented by resummation of logarithmically-enhanced contributions. These measurements can improve the physics modelling in measurements of the W boson mass, of which an updated measurement is presented based on the dataset recorded in 2011. Improvements in the knowledge of the modelling of QCD effects allow for a reanalysis employing a powerful profile-likelihood fit technique. The production rate of Z+jet events with large missing transverse momentum is used to measure the decay width of the Z boson decaying to neutrinos. The gauge sector of the electroweak theory is probed in multiboson production. Recent measurements of diboson production by the ATLAS and CMS experiments at 13 TeV and 13.6 TeV are presented. The results are compared to theoretical prediction at next-to-next to leading order in perturbative QCD. A highlight is the measurement of W-boson pair production that reaches a precision of 3%. Furthermore, measurements probing the polarisation of the electroweak gauge bosons have become experimentally accessible and set the foundation for future tests of the scalar sector of the electroweak theory. The talk ends with a summary of recent measurements of vector-boson scattering and triboson production, which are used to constrain anomalous quartic gauge couplings.