Search for supersymmetry using vector boson fusion signatures and missing transverse momentum in pp collisions at √s = 13 TeV with the ATLAS detector

This paper presents a search for supersymmetric particles in models with highly compressed mass spectra, in events consistent with being produced through vector boson fusion. The search uses 140 fb−1 of proton-proton collision data at √s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider. Events containing at least two jets with a large gap in pseudorapidity, large missing transverse momentum, and no reconstructed leptons are selected. A boosted decision tree is used to separate events consistent with the production of supersymmetric particles from those due to Standard Model backgrounds. The data are found to be consistent with Standard Model predictions. The results are interpreted using simplified models of R-parity-conserving supersymmetry in which the lightest supersymmetric partner is a bino-like neutralino with a mass similar to that of the lightest chargino and second-to-lightest neutralino, both of which are wino-like. Lower limits at 95% confidence level on the masses of next-to-lightest supersymmetric partners in this simplified model are established between 117 and 120 GeV when the lightest supersymmetric partners are within 1 GeV in mass

Search for charged Higgs bosons produced in top-quark decays or in association with top quarks and decaying via H±→τ±ντ in 13 TeV pp collisions with the ATLAS detector

Charged Higgs bosons produced either in top-quark decays or in association with a top quark, subsequently decaying via H±→τ±ντ, are searched for in 140  fb−1 of proton-proton collision data at s=13  TeV recorded with the ATLAS detector. Depending on whether the top quark is produced together with the H± decays hadronically or semileptonically, the search targets τ+jets or τ+lepton final states, in both cases with a τ-lepton decaying into a neutrino and hadrons. No significant excess over the Standard Model background expectation is observed. For the mass range of 80≤mH±≤3000  GeV, upper limits at 95% confidence level are set on the production cross section of the charged Higgs boson times the branching fraction B(H±→τ±ντ) in the range 4.5 pb–0.4 fb. In the mass range 80–160 GeV, assuming the Standard Model cross section for tt¯ production, this corresponds to upper limits between 0.27% and 0.02% on B(t→bH±)×B(H±→τ±ντ).</jats:p

Measurement of double-differential charged-current Drell-Yan cross-sections at high transverse masses in pp collisions at √s = 13 TeV with the ATLAS detector

This paper presents a first measurement of the cross-section for the charged-current Drell-Yan process $pp\rightarrow W^{\pm} \rightarrow \ell^{\pm} \nu$ above the resonance region, where $\ell$ is an electron or muon. The measurement is performed for transverse masses, $m_{\text{T}}^{\text{W}}$, between 200 GeV and 5000 GeV, using a sample of 140 fb$^{-1}$ of $pp$ collision data at a centre-of-mass energy of $\sqrt{s}$ = 13 TeV collected by the ATLAS detector at the LHC during 2015-2018. The data are presented single differentially in transverse mass and double differentially in transverse mass and absolute lepton pseudorapidity. A test of lepton flavour universality shows no significant deviations from the Standard Model. The electron and muon channel measurements are combined to achieve a total experimental precision of 3% at low $m_{\text{T}}^{\text{W}}$. The single- and double differential $W$-boson charge asymmetries are evaluated from the measurements. A comparison to next-to-next-to-leading-order perturbative QCD predictions using several recent parton distribution functions and including next-to-leading-order electroweak effects indicates the potential of the data to constrain parton distribution functions. The data are also used to constrain four fermion operators in the Standard Model Effective Field Theory formalism, in particular the lepton-quark operator Wilson coefficient $c_{\ell q}^{(3)}.