46 research outputs found

    Simulation Studies of a Hybrid Network in Order to Enhance the Performance of Hybrid Internet Service

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    The work reported here addresses the modeling and simulation of a hybrid network that conforms to Hybrid Internet Service, which is an Internet access currently commercialized by Hughes Network Systems. The objective is to research and discover performance enhancement techniques for Hybrid Internet Service. Hybrid Internet Service intends to provide Internet end users with high bandwidth by delivering packets over a satellite channel. It takes advantage of the fact that the vast majority of Internet end-users don't send as much data as they receive. However, long delays experienced over the satellite channel (in the case of a GEO satellite) have catastrophic consequences on the overall throughput with Commercial-Off-The-Shelf TPC/IP stacks. This problem is addressed by the Asymmetric TCP/IP protocol implemented within a gateway, the hybrid gateway. The hybrid gateway acts as a go-between for the server and the end user. The hybrid gateway both acknowledges packets on behalf of the end user and advertises a larger window to the server. We have implemented the Asymmetric TCP/IP within the hybrid gateway with OPNET, which is an industrial-strength, popular network modeling and simulation software. A discussion of the current results of the simulation in the broader perspective of hybrid networks development is provided following the presentation of both Hybrid Internet Service and OPNET along with the various built-in OPNET models used in the course of the simulation. The methodology we have followed is also included in this report

    Measurement of vector boson production cross sections and their ratios using pp collisions at s=13.6 TeV with the ATLAS detector

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    Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum

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    Measurements of electroweak W±Z boson pair production in association with two jets in pp collisions at √s = 13 TeV with the ATLAS detector

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    Measurements of integrated and differential cross-sections for electroweak W±Z production in association with two jets (W±Zjj) in proton-proton collisions are presented. The data collected by the ATLAS detector at the Large Hadron Collider from 2015 to 2018 at a centre-of-mass energy of √ s = 13 TeV are used, corresponding to an integrated luminosity of 140 fb−1 . The W±Zjj candidate events are reconstructed using leptonic decay modes of the gauge bosons. Events containing three identified leptons, either electrons or muons, and two jets are selected. Processes involving pure electroweak W±Zjj production at Born level are separated from W±Zjj production involving a strong coupling. The measured integrated fiducial cross-section of electroweak W±Zjj production per lepton flavour is σW Zjj−EW→ℓ ′ νℓℓjj = 0.368 ± 0.037 (stat.) ± 0.059 (syst.) ± 0.003 (lumi.) fb, where ℓ and ℓ ′ are either an electron or a muon. Respective cross-sections of electroweak and strong W±Zjj production are measured separately for events with exactly two jets or with more than two jets, and in three bins of the invariant mass of the two jets. The inclusive W±Zjj production cross-section, without separating electroweak and strong production, is also measured to be σW Zjj→ℓ ′ νℓℓjj = 1.462 ± 0.063 (stat.) ± 0.118 (syst.) ± 0.012 (lumi.) fb, per lepton flavour. The inclusive W±Zjj production cross-section is measured differentially for several kinematic observables. Finally, the measurements are used to constrain anomalous quartic gauge couplings by extracting 95% confidence level intervals on dimension-8 operators

    Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum

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    Inelastic beam-gas collisions at the Large Hadron Collider (LHC), within a few hundred metres of the ATLAS experiment, are known to give the dominant contribution to beam backgrounds. These are monitored by ATLAS with a dedicated Beam Conditions Monitor (BCM) and with the rate of fake jets in the calorimeters. These two methods are complementary since the BCM probes backgrounds just around the beam pipe while fake jets are observed at radii of up to several metres. In order to quantify the correlation between the residual gas density in the LHC beam vacuum and the experimental backgrounds recorded by ATLAS, several dedicated tests were performed during LHC Run 2. Local pressure bumps, with a gas density several orders of magnitude higher than during normal operation, were introduced at different locations. The changes of beam-related backgrounds, seen in ATLAS, are correlated with the local pressure variation. In addition the rates of beam-gas events are estimated from the pressure measurements and pressure bump profiles obtained from calculations. Using these rates, the efficiency of the ATLAS beam background monitors to detect beam-gas events is derived as a function of distance from the interaction point. These efficiencies and characteristic distributions of fake jets from the beam backgrounds are found to be in good agreement with results of beam-gas simulations performed with theFluka Monte Carlo programme

    Measurement of vector boson production cross sections and their ratios using pp collisions at √s = 13.6 TeV with the ATLAS detector

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    Abstract available from publisher's website

    Searches for exclusive Higgs boson decays into D⁎γ and Z boson decays into D0γ and Ks0γ in pp collisions at √s = 13 TeV with the ATLAS detector

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    Searches for exclusive decays of the Higgs boson into D⁎γ and of the Z boson into D0γ and Ks0γ can probe flavour-violating Higgs boson and Z boson couplings to light quarks. Searches for these decays are performed with a pp collision data sample corresponding to an integrated luminosity of 136.3 fb−1 collected at s=13TeV between 2016–2018 with the ATLAS detector at the CERN Large Hadron Collider. In the D⁎γ and D0γ channels, the observed (expected) 95% confidence-level upper limits on the respective branching fractions are B(H→D⁎γ)<1.0(1.2)×10−3, B(Z→D0γ)<4.0(3.4)×10−6, while the corresponding results in the Ks0γ channel are B(Z→Ks0γ)<3.1(3.0)×10−6

    Search for heavy Majorana neutrinos in e±e± and e±μ± final states via WW scattering in pp collisions at √s = 13 TeV with the ATLAS detector

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    A search for heavy Majorana neutrinos in scattering of same-sign W boson pairs in proton–proton collisions at √s = 13 TeV at the LHC is reported. The dataset used corresponds to an integrated luminosity of 140 fb−1, collected with the ATLAS detector during 2015–2018. The search is performed in final states including a same-sign ee or eμ pair and at least two jets with large invariant mass and a large rapidity difference. No significant excess of events with respect to the Standard Model background predictions is observed. The results are interpreted in a benchmark scenario of the Phenomenological Type-I Seesaw model. New constraints are set on the values of the |VeN|2 and |VeN V*μN| parameters for heavy Majorana neutrino masses between 50 GeV and 20 TeV, where VℓN is the matrix element describing the mixing of the heavy Majorana neutrino mass eigenstate with the Standard Model neutrino of flavour ℓ = e, μ. The sensitivity to the Weinberg operator is investigated and constraints on the effective ee and eμ Majorana neutrino masses are reported. The statistical combination of the ee and eμ channels with the previously published μμ channel is performed

    Somali women’s political participation and leadership-evidence and opportunities

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    This report synthesises findings from an eleven month qualitative research project (August 2016 - June 2017), carried out by Social Development Direct and Forcier Consulting, and funded by the Research and Evidence Division (RED) within the UK government’s Department for International Development (DFID). The research aims to provide evidence on the principal enabling and constraining factors for Somali women’s participation and leadership in government and political structures, and offers insight on the strategies and circumstances under which Somali women have, and have not, accessed and influenced within these spaces
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