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We present the first measurements of nitryl chloride (ClNO2) over continental Europe. Significant quantities of ClNO2, up to 800 pptv, were measured at a mountaintop field site in Hessen, southwest Germany. ClNO2 was detected during the majority of nights between the 15th August and 16th September 2011, its largest mixing ratios being associated with air masses influenced by sea salt and anthropogenic NOx emissions. ClNO2 persisted in measurable quantities until early afternoons on days with low photolysis frequencies. As a consequence, early morning production rates of Cl atoms could significantly exceed the production of OH via ozone photolysis, likely leading to increased O3 production. Key Points Nitryl chloride exists in significant mixing fractions over Europe Nitryl chloride is likely of marine origin, deriving from aged sea salt and N2O5 Nitryl chloride is a significant radical source in early morning

During LHC Run 2 (2015–2018) the ATLAS Level-1 topological trigger allowed efficient data-taking by the ATLAS experiment at luminosities up to 2.1×1034 cm-2s-1, which exceeds the design value by a factor of two. The system was installed in 2016 and operated in 2017 and 2018. It uses Field Programmable Gate Array processors to select interesting events by placing kinematic and angular requirements on electromagnetic clusters, jets, τ-leptons, muons and the missing transverse energy. It allowed to significantly improve the background event rejection and signal event acceptance, in particular for Higgs and B-physics processes.

Several improvements to the ATLAS triggers used to identify jets containing b-hadrons (b-jets) were implemented for data-taking during Run 2 of the Large Hadron Collider from 2016 to 2018. These changes include reconfiguring the b-jet trigger software to improve primary-vertex finding and allow more stable running in conditions with high pile-up, and the implementation of the functionality needed to run sophisticated taggers used by the offline reconstruction in an online environment. These improvements yielded an order of magnitude better light-flavour jet rejection for the same b-jet identification efficiency compared to the performance in Run 1 (2011–2012). The efficiency to identify b-jets in the trigger, and the conditional efficiency for b-jets that satisfy offline b-tagging requirements to pass the trigger are also measured. Correction factors are derived to calibrate the b-tagging efficiency in simulation to match that observed in data. The associated systematic uncertainties are substantially smaller than in previous measurements. In addition, b-jet triggers were operated for the first time during heavy-ion data-taking, using dedicated triggers that were developed to identify semileptonic b-hadron decays by selecting events with geometrically overlapping muons and jets.

A search for Higgs boson pair production in events with two $b$-jets and two $τ$-leptons is presented, using a proton–proton collision dataset with an integrated luminosity of 139 fb-1 collected at $\\sqrt{s}$ = 13 TeV by the ATLAS experiment at the LHC. Higgs boson pairs produced non-resonantly or in the decay of a narrow scalar resonance in the mass range from 251 to 1600 GeV are targeted. Events in which at least one $τ$-lepton decays hadronically are considered, and multivariate discriminants are used to reject the backgrounds. No significant excess of events above the expected background is observed in the non-resonant search. The largest excess in the resonant search is observed at a resonance mass of 1 TeV, with a local (global) significance of 3.1$σ$ (2.0$σ$). Observed (expected) 95% confidence-level upper limits are set on the non-resonant Higgs boson pair-production cross-section at 4.7 (3.9) times the Standard Model prediction, assuming Standard Model kinematics, and on the resonant Higgs boson pair-production cross-section at between 21 and 900 fb (12 and 840 fb), depending on the mass of the narrow scalar resonance.

Inclusive and differential fiducial cross sections of the Higgs boson are measured in the H → Z Z * → 4 ℓ ( ℓ = e , μ ) decay channel. The results are based on proton-proton collision data produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector from 2015 to 2018, equivalent to an integrated luminosity of 139 $\\hbox {fb}^{-1}$ fb - 1 . The inclusive fiducial cross section for the H → Z Z * → 4 ℓ process is measured to be σ fid = 3.28 ± 0.32  fb, in agreement with the Standard Model prediction of σ fid , SM = 3.41 ± 0.18  fb. Differential fiducial cross sections are measured for a variety of observables which are sensitive to the production and decay of the Higgs boson. All measurements are in agreement with the Standard Model predictions. The results are used to constrain anomalous Higgs boson interactions with Standard Model particles.

A dedicated sample of Large Hadron Collider proton-proton collision data at centre-of-mass energy √s = 8 TeV is used to study inclusive single diffractive dissociation, pp → X p. The intact final-state proton is reconstructed in the ATLAS ALFA forward spectrometer, while charged particles from the dissociated system X are measured in the central detector components. The fiducial range of the measurement is -4.0 < log10ξ < -1.6 and 0.016 < |t| < 0.43 GeV2, where ξ is the proton fractional energy loss and t is the squared four-momentum transfer. The total cross section integrated across the fiducial range is 1.59 ± 0.13 mb. Cross sections are also measured differentially as functions of ξ, t, and Δη, a variable that characterises the rapidity gap separating the proton and the system X. The data are consistent with an exponential t dependence, dσ/dt ∝ eBt with slope parameter B = 7.65 ± 0.34 GeV-2. Interpreted in the framework of triple Regge phenomenology, the ξ dependence leads to a pomeron intercept of α(0) = 1.07 ± 0.09.

This paper presents a measurement of ZZ production with the ATLAS detector at the Large Hadron Collider. The measurement is carried out in the final state with two charged leptons and two neutrinos, using data collected during 2015 and 2016 in pp collisions at $\\sqrt{s}$ = 13 TeV, corresponding to an integrated luminosity of 36.1 fb-1. The integrated cross-sections in the total and fiducial phase spaces are measured with an uncertainty of 7% and compared with Standard Model predictions, and differential measurements in the fiducial phase space are reported. No significant deviations from the Standard Model predictions are observed, and stringent constraints are placed on anomalous couplings corresponding to neutral triple gauge-boson interactions.

A search for a narrow scalar resonance decaying into an opposite-sign muon pair produced in events with and without b-tagged jets is presented in this paper. The search uses 36.1 fb-1 of $ \\sqrt{s}=13 $ TeV proton-proton collision data recorded by the ATLAS experiment at the LHC. No significant excess of events above the expected Standard Model background is observed in the investigated mass range of 0.2 to 1.0 TeV. The observed upper limits at 95% confidence level on the cross section times branching ratio for b-quark associated production and gluon-gluon fusion are between 1.9 and 41 fb and 1.6 and 44 fb respectively, which is consistent with expectations. [Figure not available: see fulltext.].

IntroductionHearing loss is highly prevalent and impacts many aspects of a person’s life, including communication, social engagement, employment, general health and well-being. Yet, many people do not access hearing healthcare and are unaware of the range of hearing healthcare options available. Barriers to hearing healthcare include poor understanding of hearing loss and its impact; poor knowledge of help-seeking for hearing healthcare options; minimal support to help decide which option is best; and stigma related to hearing loss. These barriers lead to many people not receiving the hearing healthcare they need. Guided by theories of behaviour change and implementation science, HearChoice, an online tailored decision support intervention, has been co-developed to empower adults with hearing difficulties by offering them choice and control over their own hearing healthcare. HearChoice aims to facilitate informed decisions, accessibility and uptake of hearing healthcare, including a wide range of interventions, for adults with hearing difficulties. The objectives of the trial are to evaluate the effectiveness, health economics and feasibility of HearChoice.Methods and analysisThis online randomised controlled trial will recruit participants with hearing difficulties across Australia, with an anticipated sample size of 640. Participants will be randomised to either HearChoice (treatment) or an Australia-specific Hearing Option Grid (active control), both delivered online. Outcomes will be assessed at baseline when the interventions will be offered, at 7 days post-intervention (primary endpoint) and at 3 months post-intervention. An email reminder will be sent at 1-month post-intervention. The primary outcome is decisional conflict. Secondary outcomes include measures of readiness and self-efficacy to take action, hearing-related quality of life and empowerment, assessment of the value and impact of HearChoice, work performance and health, and feasibility measures. Primary analysis will compare outcomes between HearChoice and the active control at the primary endpoint.Ethics and disseminationThe study was approved by the Curtin University Human Ethics Committee (HRE2023-0024). All participants will provide written informed consent prior to participation. A broad dissemination plan of the study findings includes peer-reviewed publications, scientific conference presentations, articles and presentations for the wider community and public written in lay and accessible language, and social media.Trial registration numberAustralian New Zealand Clinical Trials Registry (ACTRN12624001139561).