2025/07/03 by ATLAS Collaboration · 3 voices
Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #hep-ex
paper · pdf · doi:10.48550/arxiv.2507.02632
arxiv published 2025/07/03 · arxiv updated 2025/12/10
A measurement of the top-quark pole mass mtpole is presented in tt events with an additional jet, tt+1-jet, produced in pp collisions at √(s)=13 TeV. The data sample, recorded with the ATLAS experiment during Run 2 of the LHC, corresponds to an integrated luminosity of 140~fb-1. Events with one electron and one muon of opposite electric charge in the final state are selected to measure the tt+1-jet differential cross-section as a function of the inverse of the invariant mass of the tt+1-jet system. Iterative Bayesian Unfolding is used to correct the data to enable comparison with fixed-order calculations at next-to-leading-order accuracy in the strong coupling. The process pp → ttj (2 → 3), where top quarks are taken as stable particles, and the process pp → bbl+νl- ν j (2 → 7), which includes top-quark decays to the dilepton final state and off-shell effects, are considered. The top-quark mass is extracted using a χ2 fit of the unfolded normalized differential cross-section distribution. The results obtained with the 2 → 3 and 2 → 7 calculations are compatible within theoretical uncertainties, providing an important consistency check. The more precise determination is obtained for the 2 → 3 measurement: mtpole=170.7±0.3~(stat.)±1.4~(syst.)~± 0.3~(scale)~± 0.2~(PDF⊕αS)~GeV, which is in good agreement with other top-quark mass results.