CERN Accelerating science

ATLAS Slides
Report number	ATL-PHYS-SLIDE-2023-022
Title	A low Energy $t\bar{t}$ Cross-section Measurement with the ATLAS Detector
Author(s)	Singh, Sahibjeet (University of Toronto (CA)) ; Sinervo, Pekka (University of Toronto (CA)) ; Hawkings, Richard (CERN) ; Serkin, Leonid (Universidad Nacional Autonoma (MX)) ; Giuli, Francesco (CERN) ; Kareem, Mohammad (York University (CA))
Corporate author(s)	The ATLAS collaboration
Collaboration	ATLAS Collaboration
Submitted to	36th Rencontres de Physique de La Vallée d'Aoste (La Thuile 2023), La Thuile, Aosta, Italy, 5 - 11 Mar 2023
Submitted by	[email protected] on 20 Mar 2023
Subject category	Particle Physics - Experiment
Accelerator/Facility, Experiment	CERN LHC ; ATLAS
Free keywords	TOP
Abstract	The inclusive top-quark pair (tt ̅) production cross-section was measured in proton-proton collisions at a center of mass energy of 5 TeV with 257 pb^(-1) of data collected by the ATLAS detector. The tt ̅ cross-section measurement at a lower center of mass helps to further constrain the gluon Parton Distribution Function (PDF) at high Bjorken x. The cross-section is first measured individually in both the dilepton and single-lepton channels of the tt ̅ decay before being combined. The measurement in the dilepton channel is measured using a “cut-and-count” approach whereas the single-lepton measurement utilizes a Boosted Decision Tree (BDT) trained on Monte Carlo to separate signal from background. The output distribution of the BDT is the fit to data in a profile-likelihood fit leading to the single-lepton measurement being the most precise measurement of the tt ̅ cross-section measured in the single-lepton channel to date.