Search for nonresonant pair production of Higgs bosons in the <math display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> final state in <math display="inline"><mi>p</mi><mi>p</mi></math> collisions at <math display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> with the ATLAS detector

International audienceA search for nonresonant Higgs boson pair production in the bb¯bb¯ final state is presented. The analysis uses 126  fb-1 of pp collision data at s=13  TeV collected with the ATLAS detector at the Large Hadron Collider, and targets both the gluon-gluon fusion and vector-boson fusion production modes. No evidence of the signal is found and the observed (expected) upper limit on the cross section for nonresonant Higgs boson pair production is determined to be 5.4 (8.1) times the Standard Model predicted cross section at 95% confidence level. Constraints are placed on modifiers to the HHH and HHVV couplings. The observed (expected) 2σ constraints on the HHH coupling modifier, κλ, are determined to be [-3.5,11.3] ([-5.4,11.4]), while the corresponding constraints for the HHVV coupling modifier, κ2V, are [-0.0,2.1] ([-0.1,2.1]). In addition, constraints on relevant coefficients are derived in the context of the Standard Model effective field theory and Higgs effective field theory, and upper limits on the HH production cross section are placed in seven Higgs effective field theory benchmark scenarios

Combination of searches for invisible decays of the Higgs boson using 139 fb−1 of proton-proton collision data at s = 13 TeV collected with the ATLAS experiment

Many extensions of the Standard Model predict the production of dark matter particles at the LHC. Sufficiently light dark matter particles may be produced in decays of the Higgs boson that would appear invisible to the detector. This Letter presents a statistical combination of searches for H → invisible decays where multiple production modes of the Standard Model Higgs boson are considered. These searches are performed with the ATLAS detector using 139 fb−1 of proton–proton collisions at a centre–of–mass energy of √s = 13 TeV at the LHC. In combination with the results at √s = 7 TeV and 8 TeV, an upper limit on the H → invisible branching ratio of 0.107 (0.077) at the 95% confidence level is observed (expected). These results are also interpreted in the context of models where the 125 GeV Higgs boson acts as a portal to dark matter, and limits are set on the scattering cross-section of weakly interacting massive particles and nucleons

Measurements of differential cross sections of Higgs boson production through gluon fusion in the H→WW∗→eνμνH\rightarrow WW^{*}\rightarrow e\nu \mu \nu final state at s=13\sqrt{s} = 13 TeV with the ATLAS detector

International audienceHiggs boson production via gluon–gluon fusion is measured in the $WW^{*} \rightarrow e\nu \mu \nu$ decay channel. The dataset utilized corresponds to an integrated luminosity of 139 fb$^{-1}$ collected by the ATLAS detector from $\sqrt{s}=13$ TeV proton–proton collisions delivered by the Large Hadron Collider between 2015 and 2018. Differential cross sections are measured in a fiducial phase space restricted to the production of at most one additional jet. The results are consistent with Standard Model expectations, derived using different Monte Carlo generators

Studies of the muon momentum calibration and performance of the ATLAS detector with pp collisions at s=13\sqrt{s}=13 TeV

AbstractThis paper presents the muon momentum calibration and performance studies for the ATLAS detector based on the pp collisions data sample produced at $$\sqrt{s}$$ s  = 13 TeV at the LHC during Run 2 and corresponding to an integrated luminosity of 139 $${\textrm{fb}}^{-1}$$ fb - 1 . An innovative approach is used to correct for potential charge-dependent momentum biases related to the knowledge of the detector geometry, using the $$Z\rightarrow \mu ^{+}\mu ^{-}$$ Z → μ + μ - resonance. The muon momentum scale and resolution are measured using samples of $$J/\psi \rightarrow \mu ^{+}\mu ^{-}$$ J / ψ → μ + μ - and $$Z\rightarrow \mu ^{+}\mu ^{-}$$ Z → μ + μ - events. A calibration procedure is defined and applied to simulated data to match the performance measured in real data. The calibration is validated using an independent sample of $$\Upsilon \rightarrow \mu ^{+}\mu ^{-}$$ Υ → μ + μ - events. At the Z$$(J/\psi )$$ ( J / ψ ) peak, the momentum scale is measured with an uncertainty at the 0.05% (0.1%) level, and the resolution is measured with an uncertainty at the 1.5% (2%) level. The charge-dependent bias is removed with a dedicated in situ correction for momenta up to 450 GeV with a precision better than 0.03 $${\textrm{TeV}}^{-1}$$ TeV - 1 .</jats:p