Evidence of pair production of longitudinally polarised vector bosons and study of CP properties in $ZZ\to 4\ell$ events with the ATLAS detector at $\sqrt{s}=13$ TeV

Abstract

A study of the polarisation and CP properties in $ZZ$ production is presented. The used data set corresponds to an integrated luminosity of 140 fb${}^{-1}$ of proton-proton collisions at a centre-of-mass energy of $13$ TeV recorded by the ATLAS detector at the Large Hadron Collider. The $ZZ$ candidate events are reconstructed using two same-flavour opposite-charge electron or muon pairs. The production of two longitudinally polarised $Z$ bosons is measured with a significance of 4.3 standard deviations, and its cross-section is measured in a fiducial phase space to be $2.45\pm 0.60$ fb, consistent with the next-to-leading-order Standard Model prediction. The inclusive differential cross-section as a function of a CP-sensitive angular observable is also measured. The results are used to constrain anomalous CP-odd neutral triple gauge couplings.

arXiv comment46 pages in total, author list starting page 29, 8 figures, 2 tables, published in JHEP. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2021-05/

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• Electroweak, QCD and flavour physics studies with ATLAS data from Run 2 of the LHC
• Studies of the energy dependence of diboson polarization fractions and the Radiation Amplitude Zero effect in WZ production with the ATLAS detector
• $H\to Z\gamma$ decay and $CP$ violation
• $CP$ violation in the $HZZ$ vertex and left-right asymmetries
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