9 research outputs found

    Measurement of the tt¯ cross section and its ratio to the Z production cross section using pp collisions at √s = 13.6 TeV with the ATLAS detector

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    The inclusive top-quark-pair production cross section σtt¯ and its ratio to the Z-boson production cross section have been measured in proton–proton collisions at √s = 13.6 TeV, using 29 fb−1 of data collected in 2022 with the ATLAS experiment at the Large Hadron Collider. Using events with an opposite-charge electron-muon pair and b-tagged jets, and assuming Standard Model decays, the top-quark-pair production cross section is measured to be σtt¯=850±3(stat.)±18(syst.)±20(lumi.) pb. The ratio of the tt¯ and the Z-boson production cross sections is also measured, where the Z-boson contribution is determined for inclusive e+e− and μ+μ− events in a fiducial phase space. The relative uncertainty on the ratio is reduced compared to the tt¯ cross section, thanks to the cancellation of several systematic uncertainties. The result for the ratio, Rtt¯/Z=1.145±0.003(stat.)±0.021(syst.)±0.002(lumi.) is consistent with the Standard Model prediction using the PDF4LHC21 PDF set

    The use of hyperventilation therapy after traumatic brain injury in Europe: an analysis of the BrainIT database.

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    Objective To assess the use of hyperventilation and the adherence to Brain Trauma Foundation-Guidelines (BTF-G) after traumatic brain injury (TBI). Setting Twenty-two European centers are participating in the BrainIT initiative. Design Retrospective analysis of monitoring data. Patients and participants One hundred and fifty-one patients with a known time of trauma and at least one recorded arterial blood–gas (ABG) analysis. Measurements and results A total number of 7,703 ABGs, representing 2,269 ventilation episodes (VE) were included in the analysis. Related minute-by-minute ICP data were taken from a 30 min time window around each ABG collection. Data are given as mean with standard deviation. (1) Patients without elevated intracranial pressure (ICP) (<20 mmHg) manifested a statistically significant higher PaCO2 (36 ± 5.7 mmHg) in comparison to patients with elevated ICP (≥20 mmHg; PaCO2: 34 ± 5.4 mmHg, P < 0.001). (2) Intensified forced hyperventilation (PaCO2 ≤ 25 mmHg) in the absence of elevated ICP was found in only 49 VE (2%). (3) Early prophylactic hyperventilation (<24 h after TBI; PaCO2 ≤ 35 mmHg, ICP < 20 mmHg) was used in 1,224 VE (54%). (4) During forced hyperventilation (PaCO2 ≤ 30 mmHg), simultaneous monitoring of brain tissue pO2 or SjvO2 was used in only 204 VE (9%). Conclusion While overall adherence to current BTF-G seems to be the rule, its recommendations on early prophylactic hyperventilation as well as the use of additional cerebral oxygenation monitoring during forced hyperventilation are not followed in this sample of European TBI centers.J.-O. Neumann, I. R. Chambers, G. Citerio, P. Enblad, B. A. Gregson, T. Howells, J. Mattern, P. Nilsson, I. Piper, A. Ragauskas, J. Sahuquillo, Y. H. Yau, K. Kiening on behalf of the BrainIT Grou
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