Scientific diving in Brazil: history, present and perspectives

Scientific diving (SD) is defined as any diving activity that applies scientific procedures to produce subsidies forstudies and technical works in underwater environments. The first report of an underwater scientific study inBrazil dates to the 19th century, in the Abrolhos reefs. Currently, in Brazil, scientific diving has been performedin various areas, from shallow coastal regions to remote and sometimes hard-to-reach places, such as oceanicislands, flooded caves, and icy areas like Antarctica. However, the regulation of SD in Brazil still lacks moreconcrete actions towards an effective and efficient self-regulation that offers physical safety to practitioners andinstitutional safeguards for organizations that use it in their research projects. Thus, this article aims to contributeto a better understanding of this critical issue in Brazil and to serve as a reference and incentive for the trainingof professionals and the development of these activities in the country. It includes: 1) a historical review ofSD; 2) a diagnosis of the training and application of SD in Brazil; 3) the evolution of marine sciences in Brazilfrom the perspective of SD; 4) a review of the use of environmental assessment and underwater conservationtechniques in oceans and internal waters; 5) an analysis of the evolution of scientific diver training in Brazil,including a diagnosis on training; 6) the history and updates of the rules, regulations, and safety of SD. Givenall the potential of diving combined with specific techniques for research, monitoring, and marine and limnicscience in Brazil, we aim to understand the evolution of scientific diving teaching and to outline perspectives inthe country, as it is crucial for the training of qualified scientists capable of performing these underwater tasks.Finally, we present futture plans for the development of this activity in Brazil from the point of view of researchand the labor market

Combination of searches for Higgs boson pair production in pp collisions at √s = 13 TeV with the ATLAS detector

This Letter presents results from a combination of searches for Higgs boson pair production using 126–140 fb−1 of proton-proton collision data at √s = 13 TeV recorded with the ATLAS detector. At 95% confidence level (CL), the upper limit on the production rate is 2.9 times the standard model (SM) prediction, with an expected limit of 2.4 assuming no Higgs boson pair production. Constraints on the Higgs boson self-coupling modifier κλ = λHHH=λSM HHH, and the quartic HHVV coupling modifier κ2V = gHHVV=gSM HHVV, are derived individually, fixing the other parameter to its SM value. The observed 95% CL intervals are −1.2 < κλ < 7.2 and 0.6 < κ2V < 1.5, respectively, while the expected intervals are −1.6 < κλ < 7.2 and 0.4 < κ2V < 1.6 in the SM case. Constraints obtained for several interaction parameters within Higgs effective field theory are the strongest to date, offering insights into potential deviations from SM predictions

Combination of searches for Higgs boson decays into a photon and a massless dark photon using pp collisions at √s = 13 TeV with the ATLAS detector

A combination of searches for Higgs boson decays into a visible photon and a massless dark photon (H → γγd) is presented using 139 fb−1 of proton-proton collision data at a centre-of-mass energy of √s = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. The observed (expected) 95% confidence level upper limit on the Standard Model Higgs boson decay branching ratio is determined to be B(H → γγd) < 1.3% (1.5)%. The search is also sensitive to higher-mass Higgs bosons decaying into the same final state. The observed (expected) 95% confidence level limit on the cross-section times branching ratio ranges from 16 fb (20 fb) for mH = 400 GeV to 1.0 fb (1.5 fb) for mH = 3 TeV. Results are also interpreted in the context of a minimal simplified model

Search for decays of the Higgs boson into a pair of pseudoscalar particles decaying into bb¯τ+τ− using pp collisions at √s = 13 TeV with the ATLAS detector

This paper presents a search for exotic decays of the Higgs boson into a pair of new pseudoscalar particles, H → aa, where one pseudoscalar decays into a b-quark pair and the other decays into a τ-lepton pair, in the mass range 12 ≤ ma ≤ 60 GeV. The analysis uses pp collision data at √s = 13 TeV collected with the ATLAS detector at the LHC, corresponding to an integrated luminosity of 140 fb−1. No significant excess above the Standard Model (SM) prediction is observed. Assuming the SM Higgs boson production cross section, the search sets upper limits at 95% confidence level on the branching ratio of Higgs bosons decaying into bb¯ τ+τ−, B(H → aa → bb¯ τ+τ−), between 2.2% and 3.9% depending on the pseudoscalar mass

Measurement of single top-quark production in association with a W boson in pp collisions at √s = 13 TeV with the ATLAS detector

The inclusive cross section for the production of a single top quark in association with a W boson is measured using 140 fb−1 of proton-proton collision data collected with the ATLAS detector at √s = 13 TeV. Events containing two charged leptons and at least one jet identified as originating from a b-quark are selected. A multivariate discriminant is constructed to separate the tW signal from the t¯t background. The cross section is extracted using a profile likelihood fit to the signal and control regions and it is measured to be σtW = 75+15 −14 pb, in good agreement with the Standard Model prediction. The measured cross section is used to extract a value for the left-handed form factor at the Wtb vertex times the Cabibbo-Kobayashi-Maskawa matrix element |fLVVtb| of 0.97 0.10

Search for dark mesons decaying to top and bottom quarks in proton-proton collisions at √s = 13 TeV with the ATLAS detector

A search for dark mesons originating from strongly-coupled, SU(2) dark favor symmetry conserving models and decaying gaugephobically to pure Standard Model final states containing top and bottom quarks is presented. The search targets fully hadronic final states and final states with exactly one electron or muon and multiple jets. The analyzed data sample corresponds to an integrated luminosity of 140 fb−1 of proton-proton collisions collected at √s = 13 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess over the Standard Model background expectation is observed and the results are used to set the first direct constraints on this type of model. The two-dimensional signal space of dark pion masses mπD and dark rho-meson masses mρD is scanned. For mπD /mρD = 0.45, dark pions with masses mπD < 940 GeV are excluded at the 95% CL, while for mπD /mρD = 0.25 masses mπD < 740 GeV are excluded

Search for a resonance decaying into a scalar particle and a Higgs boson in final states with leptons and two photons in proton-proton collisions at √s = 13 TeV with the ATLAS detector

A search for a hypothetical heavy scalar particle, X, decaying into a singlet scalar particle, S, and a Standard Model Higgs boson, H, using 140 fb−1 of proton-proton collision data at the centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the LHC is presented. The explored mass range is 300 ≤ mX ≤ 1000 GeV and 170 ≤ mS ≤ 500 GeV. The signature of this search is one or two leptons (e or µ) from the decay of vector bosons originating from the S particle, S → W±W∓/ZZ, and two photons from the Higgs boson decay, H → γγ. No significant excess is observed above the expected Standard Model background. The observed (expected) upper limits at the 95% confidence level on the cross-section for gg → X → SH, assuming the same S → WW/ZZ branching ratios as for a SM-like heavy Higgs boson, are between 530 (800) fb and 120 (170) fb

Search for dark mesons decaying to top and bottom quarks in proton-proton collisions at √s = 13 TeV with the ATLAS detector

A search for dark mesons originating from strongly-coupled, SU(2) dark favor symmetry conserving models and decaying gaugephobically to pure Standard Model final states containing top and bottom quarks is presented. The search targets fully hadronic final states and final states with exactly one electron or muon and multiple jets. The analyzed data sample corresponds to an integrated luminosity of 140 fb−1 of proton-proton collisions collected at √s = 13 TeV with the ATLAS detector at the Large Hadron Collider. No significant excess over the Standard Model background expectation is observed and the results are used to set the first direct constraints on this type of model. The two-dimensional signal space of dark pion masses mπD and dark rho-meson masses mρD is scanned. For mπD /mρD = 0.45, dark pions with masses mπD < 940 GeV are excluded at the 95% CL, while for mπD /mρD = 0.25 masses mπD < 740 GeV are excluded