Speaker
Description
A measurement of the ratio between the top-quark-pair and $Z$-boson production cross-sections, using data corresponding to an integrated luminosity of $1.2~\text{fb}^{-1}$, collected by the ATLAS detector in 2022 during the early Run 3 of the Large Hadron Collider (LHC) in proton-proton collisions with a centre-of-mass energy of $13.6$ TeV, is presented.
This measurement is sensitive to different Standard Model variables, such as the strong coupling constant and top-quark mass, as well as the parton distribution function ratio of quarks and gluons.
The analysis uses dileptonic events with two leptons of opposite charge. To target the top-quark pair events, electron-muon pairs are selected and events with $b$-tagged jets are used. For the $Z$-boson events, electron-electron and muon-muon events are used that are inclusive in jet multiplicity.
The cross-section ratio is determined using a profile-likelihood method that also includes a measurement of the efficiency to reconstruct and tag $b$-jets in the top-quark pair events in-situ. Further, the ratio setup of the analysis allows for a large cancellation of the luminosity uncertainty, which would otherwise dominate results in such an early stage of the data-taking in LHC Run 3. The results of this analysis validate the data quality, hardware and software updates.
| Title | Measurement of the top-quark pair to $Z$-boson production cross-section ratio at a centre-of-mass energy of 13.6 TeV with the ATLAS detector |
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