During January 2014, an industrial solvent contaminated West Virginia’s Elk River and 15% of the state population’s tap water. A rapid in-home survey and water testing was conducted 2 weeks following the spill to understand resident perceptions, tap water chemical levels, and premise plumbing flushing effectiveness. Water odors were detected in all 10 homes sampled before and after premise plumbing flushing. Survey and medical data indicated flushing caused adverse health impacts. Bench-scale experiments and physiochemical property predictions showed flushing promoted chemical volatilization, and contaminants did not appreciably sorb into cross-linked polyethylene (PEX) pipe. Flushing reduced tap water 4-methylcyclohexanemethanol (4-MCHM) concentrations within some but not all homes. 4-MCHM was detected at unflushed (<10 to 420 μg/L) and flushed plumbing systems (<10 to 96 μg/L) and sometimes concentrations differed among faucets within each home. All waters contained less 4-MCHM than the 1000 μg/L Centers for Disease Control drinking water limit, but one home exceeded the 120 μg/L drinking water limit established by independent toxicologists. Nearly all households refused to resume water use activities after flushing because of water safety concerns. Science based flushing protocols should be developed to expedite recovery, minimize health impacts, and reduce concentrations in homes when future events occur.

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Measurements of Higgs boson production cross-sections are carried out in the diphoton decay channel using 139 fb−1 of pp collision data at $$ \sqrt{s} $$ s = 13 TeV collected by the ATLAS experiment at the LHC. The analysis is based on the definition of 101 distinct signal regions using machine-learning techniques. The inclusive Higgs boson signal strength in the diphoton channel is measured to be $$ {1.04}_{-0.09}^{+0.10} $$ 1.04 − 0.09 + 0.10 . Cross-sections for gluon-gluon fusion, vector-boson fusion, associated production with a W or Z boson, and top associated production processes are reported. An upper limit of 10 times the Standard Model prediction is set for the associated production process of a Higgs boson with a single top quark, which has a unique sensitivity to the sign of the top quark Yukawa coupling. Higgs boson production is further characterized through measurements of Simplified Template Cross-Sections (STXS). In total, cross-sections of 28 STXS regions are measured. The measured STXS cross-sections are compatible with their Standard Model predictions, with a p-value of 93%. The measurements are also used to set constraints on Higgs boson coupling strengths, as well as on new interactions beyond the Standard Model in an effective field theory approach. No significant deviations from the Standard Model predictions are observed in these measurements, which provide significant sensitivity improvements compared to the previous ATLAS results.

This paper presents direct searches for lepton flavour violation in Higgs boson decays, H → eτ and H → μτ, performed using data collected with the ATLAS detector at the LHC. The searches are based on a data sample of proton-proton collisions at a centre-of-mass energy $$ \sqrt{s} $$ s = 13 TeV, corresponding to an integrated luminosity of 138 fb−1. Leptonic (τ → ℓνℓντ) and hadronic (τ → hadrons ντ) decays of the τ-lepton are considered. Two background estimation techniques are employed: the MC-template method, based on data-corrected simulation samples, and the Symmetry method, based on exploiting the symmetry between electrons and muons in the Standard Model backgrounds. No significant excess of events is observed and the results are interpreted as upper limits on lepton-flavour-violating branching ratios of the Higgs boson. The observed (expected) upper limits set on the branching ratios at 95% confidence level, $$ \mathcal{B} $$ B (H → eτ) < 0.20% (0.12%) and $$ \mathcal{B} $$ B (H → μτ ) < 0.18% (0.09%), are obtained with the MC-template method from a simultaneous measurement of potential H → eτ and H → μτ signals. The best-fit branching ratio difference, $$ \mathcal{B} $$ B (H → μτ) → $$ \mathcal{B} $$ B (H → eτ), measured with the Symmetry method in the channel where the τ-lepton decays to leptons, is (0.25 ± 0.10)%, compatible with a value of zero within 2.5σ.

Differential and double-differential distributions of kinematic variables of leptons from decays of top-quark pairs ($$ t\overline{t} $$ t t ¯ ) are measured using the full LHC Run 2 data sample collected with the ATLAS detector. The data were collected at a pp collision energy of $$ \sqrt{s} $$ s = 13 TeV and correspond to an integrated luminosity of 140 fb−1. The measurements use events containing an oppositely charged eμ pair and b-tagged jets. The results are compared with predictions from several Monte Carlo generators. While no prediction is found to be consistent with all distributions, a better agreement with measurements of the lepton pT distributions is obtained by reweighting the $$ t\overline{t} $$ t t ¯ sample so as to reproduce the top-quark pT distribution from an NNLO calculation. The inclusive top-quark pair production cross-section is measured as well, both in a fiducial region and in the full phase-space. The total inclusive cross-section is found to be$$ {\sigma}_{t\overline{t}}=829\pm 1\ \left(\textrm{stat}\right)\pm 13\ \left(\textrm{syst}\right)\pm 8\ \left(\textrm{lumi}\right)\pm 2\ \left(\textrm{beam}\right)\ \textrm{pb}, $$ σ t t ¯ = 829 ± 1 stat ± 13 syst ± 8 lumi ± 2 beam pb , where the uncertainties are due to statistics, systematic effects, the integrated luminosity and the beam energy. This is in excellent agreement with the theoretical expectation.