Mesure de la masse du quark top dans des événements tt avec un Jpsi ou un méson D dans l'état final avec les données du Run 2 de l'expérience ATLAS auprès du LHC

The ATLAS collaboration has collected from 2015 to 2018 proton-proton collisions at an energy in the center of mass of 13 TeV produced at the large hadron collider (LHC) at CERN. These data allow to study the standard model of particle physics. The main motivation for this thesis is to obtain a measurement as precise as possible of the top quark mass, from the study of pairs of top-antitop quarks decaying in the lepton+jets channel, using the mesons Jpsi, D0 or D* originating from one of the b quark in the final state. The top quark mass is thus measured to be : mtop = 173.50 +/- 0.56 (stat.) +/- 1.61 GeV (syst.) = 173.50 +/- 1.61 GeV. Other studies have been undertaken on radiation damage effects on the pixel detector of the tracking system, on the b quark fragmentation and on the expected precision on the top quark mass at the end of the high luminosity period of the LHC in 2035.La collaboration ATLAS a collecté de 2015 à 2018 des collisions protons-protons à une énergie dans le centre de masse de 13 TeV auprès du grand collisonneur de hadrons (LHC) du CERN. Ces données permettent d'étudier le modèle standard de la physique des particules. La motivation majeure de cette thèse est la mesure la plus précise possible de la masse du quark top à partir de l'étude de paires de quarks top-antitop se désintégrant dans le canal lepton+jets, en utilisant des mésons Jpsi, D0 ou D*, issus de la désintégration d'un des quarks b. La masse du quark top ainsi mesurée est : mtop = 173,50 +/- 0,56 (stat.) +/- 1,51 GeV (syst.) = 173,50 +/- 1,61 GeV. D'autres études ont été menées sur l'endommagement par rayonnement du détecteur à pixels du trajectographe interne, sur la fragmentation du quark b ainsi que sur la précision attendue sur la masse du quark top à la fin de la période de haute luminosité du LHC en 2035

Top quark mass measurement in tt events with a Jpsi or D meson in the final state with the Run 2 data of the ATLAS experiment at the LHC

La collaboration ATLAS a collecté de 2015 à 2018 des collisions protons-protons à une énergie dans le centre de masse de 13 TeV auprès du grand collisonneur de hadrons (LHC) du CERN. Ces données permettent d'étudier le modèle standard de la physique des particules. La motivation majeure de cette thèse est la mesure la plus précise possible de la masse du quark top à partir de l'étude de paires de quarks top-antitop se désintégrant dans le canal lepton+jets, en utilisant des mésons Jpsi, D0 ou D*, issus de la désintégration d'un des quarks b. La masse du quark top ainsi mesurée est : mtop = 173,50 +/- 0,56 (stat.) +/- 1,51 GeV (syst.) = 173,50 +/- 1,61 GeV. D'autres études ont été menées sur l'endommagement par rayonnement du détecteur à pixels du trajectographe interne, sur la fragmentation du quark b ainsi que sur la précision attendue sur la masse du quark top à la fin de la période de haute luminosité du LHC en 2035.The ATLAS collaboration has collected from 2015 to 2018 proton-proton collisions at an energy in the center of mass of 13 TeV produced at the large hadron collider (LHC) at CERN. These data allow to study the standard model of particle physics. The main motivation for this thesis is to obtain a measurement as precise as possible of the top quark mass, from the study of pairs of top-antitop quarks decaying in the lepton+jets channel, using the mesons Jpsi, D0 or D* originating from one of the b quark in the final state. The top quark mass is thus measured to be : mtop = 173.50 +/- 0.56 (stat.) +/- 1.61 GeV (syst.) = 173.50 +/- 1.61 GeV. Other studies have been undertaken on radiation damage effects on the pixel detector of the tracking system, on the b quark fragmentation and on the expected precision on the top quark mass at the end of the high luminosity period of the LHC in 2035

Modeling Radiation Damage to Pixel Sensors in the ATLAS Detector

Silicon pixel detectors are at the core of the current and planned upgrade of the ATLAS detector at the Large Hadron Collider (LHC). As the closest detector component to the interaction point, these detectors will be subjected to a significant amount of radiation over their lifetime: prior to the High- Luminosity LHC (HL-LHC), the innermost layers will receive a fluence in excess of 10^{15} n_{eq}/cm2 and the HL-HLC detector upgrades must cope with an order of magnitude higher fluence integrated over their lifetimes. Simulating radiation damage is critical in order to make accurate predictions for current future detector performance that will enable searches for new particles and forces as well as precision measurements of Standard Model particles such as the Higgs boson. We present a digitization model that includes radiation damage effects to the ATLAS pixel sensors for the first time and considers both planar and 3D sensor designs. In addition to describing the setup, we compare predictions for basic pixel cluster properties with real data collected at LHC proton-proton collisions

Towards a realistic track reconstruction algorithm based on graph neural networks for the HL-LHC

The physics reach of the HL-LHC will be limited by how efficiently the experiments can use the available computing resources, i.e. affordable software and computing are essential. The development of novel methods for charged particle reconstruction at the HL-LHC incorporating machine learning techniques or based entirely on machine learning is a vibrant area of research. In the past two years, algorithms for track pattern recognition based on graph neural networks (GNNs) have emerged as a particularly promising approach. Previous work mainly aimed at establishing proof of principle. In the present document we describe new algorithms that can handle complex realistic detectors. The new algorithms are implemented in ACTS, a common framework for tracking software. This work aims at implementing a realistic GNN-based algorithm that can be deployed in an HL-LHC experiment

Multi-drug resistant Acinetobacter species: a seven-year experience from a tertiary care center in Lebanon

Abstract Background Acinetobacter species have become increasingly common in the intensive care units (ICU) over the past two decades, causing serious infections. At the American University of Beirut Medical Center, the incidence of multi-drug resistant Acinetobacter baumannii (MDR-Ab) infections in the ICU increased sharply in 2007 by around 120%, and these infections have continued to cause a serious problem to this day. Methods We conducted a seven-year prospective cohort study between 2007 and 2014 in the ICU. Early in the epidemic, a case-control study was performed that included MDR-Ab cases diagnosed between 2007 and 2008 and uninfected controls admitted to the ICU during the same time. Results The total number of patients with MDR-Ab infections diagnosed between 2007 and 2014 was 128. There were also 99 patients with MDR-Ab colonization without evidence of active infection between 2011 and 2014. The incidence of MDR-Ab transmission was 315.4 cases/1000 ICU patient-days. The majority of infections were considered hospital-acquired (84%) and most consisted of respiratory infections (53.1%). The mortality rate of patients with MDR-Ab ranged from 52% to 66%. Conclusion MDR-Ab infections mostly consisted of ventilator-associated pneumonia and were associated with a very high mortality rate. Infection control measures should be reinforced to control the transmission of these organisms in the ICU