A FB in the SMEFT: precision Z physics at the LHC

• DOI: 10.1007/jhep08(2021)021
• Publication Date: 2021-08-05T19:02:46Z
• Authors: Víctor Bresó-Pla; Adam Falkowski; Martín González-A...
• Keywords: p p: scattering; angular distribution: asymmetry; FOS: Physical sciences; QC770-798; 530; 01 natural sciences; quark; Z0: production; effective field theory; High Energy Physics - Phenomenology (hep-ph); flat direction; Nuclear and particle physics. Atomic energy. Radioactivity; 0103 physical sciences; electroweak interaction; precision measurement; new physics; CERN LEP Stor; Effective Field Theories; correction: vertex; High Energy Physics - Phenomenology; p p --> lepton+ lepton-; CERN LHC Coll; [PHYS.HPHE]Physics [physics]/High Energy Physics - Phenomenology [hep-ph]; Beyond Standard Model

Abstract We study the forward-backward asymmetry AFB in pp → ℓ+ℓ− at the Z peak within the Standard Model Effective Field Theory (SMEFT). We find that this observable provides per mille level constraints on the vertex corrections of the Z boson to quarks, which close a flat direction in the electroweak precision SMEFT fit. Moreover, we show that current AFB data is precise enough so that its inclusion in the fit improves significantly LEP bounds even in simple New Physics setups. This demonstrates that the LHC can compete with and complement LEP when it comes to precision measurements of the Z boson properties.