Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Aparelho de amplificação sonora individual: melhora a sensação de zumbido? Hearing aid: does it reduce the sensation of tinnitus?

OBJETIVO: observar se o uso da amplificação sonora além de garantir melhora na inteligibilidade de fala pode proporcionar alívio na sensação de zumbido. MÉTODOS: participaram do presente estudo 21 indivíduos, usuários de aparelho de amplificação sonora individual (AASI) que referiam sensação de zumbido, além da perda auditiva sensorioneural, sendo 13 (61,9%) indivíduos do sexo feminino e oito (38,1%) do sexo masculino. A idade dos participantes variou entre 35 a 88 anos, com idade média de 61 anos. Para a avaliação dos participantes foi utilizado um questionário específico. Os dados foram analisados por meio de análise estatística descritiva e para tanto foram utilizados os testes não paramétricos: qui-quadrado e Kruskal-Wallis H. RESULTADOS: Entre os 21 participantes, 17 (80,9%) apresentaram melhora do zumbido, enquanto quatro (19,1%) referiram que o aparelho de amplificação não gerou nenhum efeito sobre o sintoma apresentado. CONCLUSÃO: este estudo verificou que a utilização do AASI reduziu imediatamente a sensação de zumbido apresentada na população estudada.<br>PURPOSE: to observe if the use of hearing aid may provide relief in tinnitus sensation besides guarantying the improvement of speech intelligibility. METHODS: a sample was made up by 21 hearing aid users and a specific questionnaire was used for the evaluation of the participants. The ages ranged from 35 to 88-year old, with an average of 61-year old. The tinnitus sensation was mentioned by 13 (61.9%) female beings and eight (38.1%) male beings beyond sensory neural hearing loss. The results were obtained through a descriptive statistical analysis, and furthermore, non-parametric tests were used, such as chi-square and Kruskal-Wallis H. RESULTS: among the participants 17 (80.9%) showed recovery from tinnitus, while four (19.1%) said that the hearing aid device did not cause any effect on the evidenced symptoms. CONCLUSION: this study found out that the usage of the hearing aid reduced promptly the sensation of tinnitus in the studied subjects

Combinations of single-top-quark production cross-section measurements and |fLVVtb| determinations at √s = 7 and 8 TeV with the ATLAS and CMS experiments

This paper presents the combinations of single-top-quark production cross-section measurements by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at s√ = 7 and 8 TeV corresponding to integrated luminosities of 1.17 to 5.1 fb−1 at s√ = 7 TeV and 12.2 to 20.3 fb−1 at s√ = 8 TeV. These combinations are performed per centre-of-mass energy and for each production mode: t-channel, tW, and s-channel. The combined t-channel cross-sections are 67.5 ± 5.7 pb and 87.7 ± 5.8 pb at s√ = 7 and 8 TeV respectively. The combined tW cross-sections are 16.3 ± 4.1 pb and 23.1 ± 3.6 pb at s√ = 7 and 8 TeV respectively. For the s-channel cross-section, the combination yields 4.9 ± 1.4 pb at s√ = 8 TeV. The square of the magnitude of the CKM matrix element Vtb multiplied by a form factor fLV is determined for each production mode and centre-of-mass energy, using the ratio of the measured cross-section to its theoretical prediction. It is assumed that the top-quark-related CKM matrix elements obey the relation |Vtd|, |Vts| ≪ |Vtb|. All the |fLVVtb|2 determinations, extracted from individual ratios at s√ = 7 and 8 TeV, are combined, resulting in |fLVVtb| = 1.02 ± 0.04 (meas.) ± 0.02 (theo.). All combined measurements are consistent with their corresponding Standard Model predictions

Searches for the ZγZ\gamma decay mode of the Higgs boson and for new high-mass resonances in pppp collisions at s=13\sqrt{s} = 13 TeV with the ATLAS detector

International audienceThis article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, exploiting Z boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb$^{−1}$ of pp collisions at $\sqrt{s}=13$ recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model pp → H → Zγ production and decay) upper limit on the production cross section times the branching ratio for pp → H → Zγ is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level

Searches for the ZγZ\gamma decay mode of the Higgs boson and for new high-mass resonances in pppp collisions at s=13\sqrt{s} = 13 TeV with the ATLAS detector

International audienceThis article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, exploiting Z boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb$^{−1}$ of pp collisions at $\sqrt{s}=13$ recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model pp → H → Zγ production and decay) upper limit on the production cross section times the branching ratio for pp → H → Zγ is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level