Constraints on the Higgs boson self-coupling from single- and double-Higgs production with the ATLAS detector using pp collisions at s = 13 TeV
Physics Letters B Elsevier BV 843 (2023) 137745
ATLAS flavour-tagging algorithms for the LHC Run 2 pp collision dataset
The European Physical Journal C Springer 83:7 (2023) 681
Abstract:
The flavour-tagging algorithms developed by the ATLAS Collaboration and used to analyse its dataset of √s = 13 TeV pp collisions from Run 2 of the Large Hadron Collider are presented. These new tagging algorithms are based on recurrent and deep neural networks, and their performance is evaluated in simulated collision events. These developments yield considerable improvements over previous jet-flavour identification strategies. At the 77% b-jet identification efficiency operating point, light-jet (charm-jet) rejection factors of 170 (5) are achieved in a sample of simulated Standard Model tt¯ events; similarly, at a c-jet identification efficiency of 30%, a light-jet (b-jet) rejection factor of 70 (9) is obtained.Measurements of observables sensitive to colour reconnection in 𝑡𝑡¯ events with the ATLAS detector at √𝑠 = 13 TeV
The European Physical Journal C Springer 83:6 (2023) 518
Abstract:
A measurement of observables sensitive to effects of colour reconnection in top-quark pair-production events is presented using 139 fb−1 of 13 TeV proton–proton collision data collected by the ATLAS detector at the LHC. Events are selected by requiring exactly one isolated electron and one isolated muon with opposite charge and two or three jets, where exactly two jets are required to be b-tagged. For the selected events, measurements are presented for the charged-particle multiplicity, the scalar sum of the transverse momenta of the charged particles, and the same scalar sum in bins of charged-particle multiplicity. These observables are unfolded to the stable-particle level, thereby correcting for migration effects due to finite detector resolution, acceptance and efficiency effects. The particle-level measurements are compared with different colour reconnection models in Monte Carlo generators. These measurements disfavour some of the colour reconnection models and provide inputs to future optimisation of the parameters in Monte Carlo generators.Constraints on the Higgs boson self-coupling from single- and double-Higgs production with the ATLAS detector using pp collisions at √s=13 TeV
Physics Letters B Elsevier 843 (2023) 137745
Abstract:
Constraints on the Higgs boson self-coupling are set by combining double-Higgs boson analyses in the bb̅bb̅, bb̅τ+τ− and bb̅γγ decay channels with single-Higgs boson analyses targeting the γγ, ZZ∗, WW∗, τ+τ− and bb̅ decay channels. The data used in these analyses were recorded by the ATLAS detector at the LHC in proton–proton collisions at √s = 13 TeV and correspond to an integrated luminosity of 126–139 fb−1. The combination of the double-Higgs analyses sets an upper limit of μHH <2.4 at 95% confidence level on the double-Higgs production cross-section normalised to its Standard Model prediction. Combining the single-Higgs and double-Higgs analyses, with the assumption that new physics affects only the Higgs boson self-coupling (λHHH ), values outside the interval −0.4 < κλ = (λHHH /λSMHHH) < 6.3 are excluded at 95% confidence level. The combined single-Higgs and double-Higgs analyses provide results with fewer assumptions, by adding in the fit more coupling modifiers introduced to account for the Higgs boson interactions with the other Standard Model particles. In this relaxed scenario, the constraint becomes −1.4 < κλ < 6.1 at 95% CL.Search for Higgs boson pair production in the b¯bWW∗ decay mode at √s = 13 TeV with the ATLAS detector
Journal of High Energy Physics Springer Berlin Heidelberg 2019:4 (2019) 92