Measurement of Top Quark Properties at the Tevatron

We highlight the most recent top quark properties measurements performed at the Tevatron collider by the CDF and D0 experiments. The data samples used for the analyses discussed correspond to an integrated luminosity varying from 360 pb-1 to 760 pb-1.Comment: 4 pages, 6 figures. To be included in the proceedings of the 41st Rencontres de Moriond, QCD and Hadronic Interactions, La Thuile, Italy, 18-25 Mar 200

Methylation-dependent DNA discrimination in natural transformation of Campylobacter jejuni

Campylobacter jejuni is naturally transformable but is selective in the DNA used in transformation. Natural transformation allows for rapid adaptation and provides a means for DNA repair, both of which enhance bacterial fitness. Our work demonstrates that the methylation status of C. jejuni DNA is critical for transformation; methylation of a single 6-bp sequence in proximity to the transforming DNA is sufficient to allow nontransforming DNA to transform C. jejuni. Our data argue against previously described means for DNA discrimination; specifically, there is no evidence that a restriction enzyme recognizes the unmodified 6-bp sequence, and no evidence of a typical DNA uptake sequence. Therefore, we have identified a distinct DNA discrimination mechanism in Campylobacter

'Etudes des états finals diphoton dans l'expérience ATLAS au LHC (mesure de section efficace différentielle, découverte d'une nouvelle résonance dans la recherche du boson de Higgs et étude de ses propriétés')

Cette thèse sera centrée sur les analyses des événements diphotons dans le détecteur ATLAS. L'activité évoluera au cours du temps et couvrira différents aspects: compréhension de la réponse du détecteur, participation a la prise de données, analyse physique et recherche de signaux de physique au-delà du modèle standard.These thesis will be concentrated on the analysis of events involving two photons in the final state. The activity will evolve with time and will cover different aspects: understanding of the detector response, participation to the data taking, physics analysis and search for physics behind the Standard ModelSAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Recherche d'un boson de Higgs leger produit en association avec une paire de quarks top dans l'experience ATLAS

One of the main goals of the ATLAS experiment is the search for the Higgs boson, the last missing ingredient of the standard model, and the studies of its properties. The experiment will be based at the future proton-proton collider LHC, whose first collisions are expected in 2007. The work presented in this thesis is dedicated to the search for a Higgs boson with a mass below 200 GeV/c2, in the associated production channel pp->ttH. The identification of jets containing b-hadrons is crucial for Higgs boson and top quark studies. The tagging performances of b-jets are studied in details in the ttH, H->bb channel, in the most realistic conditions at start of data taking (reduced pixel detector, pile-up, detection ine ciencies). At 60 % b-jet efficiency, light and c-jet rejections of 80% and 7% respectively are achieved. Whereas the discovery of the Higgs boson is expected to be relatively easy, the measurement of its parameters, in particular its couplings to fermions, is more involved. The possibility of observing the Higgs boson in the ttH, H->WW(*) channel is investigated. This process is the only one to date leading to a direct measurement of the top quark Yukawa coupling in the mass range 130-200 GeV/c2. For a Higgs boson of mass 160 GeV/c2, a statistical precision of ~7% could be reached after three years of data taking at high luminosity.L'un des principaux objectifs de l'experience ATLAS est la recherche de la derniere particule manquante du modele standard, le boson de Higgs, et l'etude de ses proprietes. Cette experience sera placee aupres du futur collisionneur de protons LHC, dont le demarrage est prevu pour l'annee 2007 au CERN. Les travaux presentes dans cette these sont dedies a la recherche d'un boson de Higgs de masse inferieure a 200 GeV/c2, dans le canal de production associee pp->ttH. L'identification des jets contenant des hadrons beaux est fondamentale pour l'etude du boson de Higgs et du quark top. Les performances d'etiquetage des jets b sont etudiees en details dans le canal ttH, H->bb, et pour des conditions de fonctionnement tres proches de celles attendues au demarrage des prises de donnees, (detecteur a pixels incomplet, bruit d'empilement et inefficacites de detection). Pour une efficacite d'identifcation de jets b de 60%, les taux de rejet attendus sont de 80% pour les jets legers et 7% pour les jets c. Si la decouverte du boson de Higgs dans ATLAS semble relativement aisee, la mesure de ses parametres, et en particulier la determination des couplages aux differents fermions, est beaucoup plus delicate. Une etude de faisabilite est proposee pour un nouveau canal, ttH, H->WW(*). Ce canal est le seul qui permet une determination directe du couplage de Yukawa du quark top dans l'intervalle de masse 130-200 GeV/c2. Pour un boson de Higgs de 160 GeV/c2, la precision statistique attendue apres trois annees de prise de donnees a haute luminosite est de 7 %

Recherche d'un boson de Higgs léger produit en association avec une paire de quarks top dans l'expérience ATLAS

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocSTRASBOURG-Bib.Central Recherche (674822133) / SudocSudocFranceF

COVID-19 outcomes in patients with inflammatory rheumatic and musculoskeletal diseases treated with rituximab: a cohort study

International audienceBackground: Various observations have suggested that the course of COVID-19 might be less favourable in patients with inflammatory rheumatic and musculoskeletal diseases receiving rituximab compared with those not receiving rituximab. We aimed to investigate whether treatment with rituximab is associated with severe COVID-19 outcomes in patients with inflammatory rheumatic and musculoskeletal diseases.Methods: In this cohort study, we analysed data from the French RMD COVID-19 cohort, which included patients aged 18 years or older with inflammatory rheumatic and musculoskeletal diseases and highly suspected or confirmed COVID-19. The primary endpoint was the severity of COVID-19 in patients treated with rituximab (rituximab group) compared with patients who did not receive rituximab (no rituximab group). Severe disease was defined as that requiring admission to an intensive care unit or leading to death. Secondary objectives were to analyse deaths and duration of hospital stay. The inverse probability of treatment weighting propensity score method was used to adjust for potential confounding factors (age, sex, arterial hypertension, diabetes, smoking status, body-mass index, interstitial lung disease, cardiovascular diseases, cancer, corticosteroid use, chronic renal failure, and the underlying disease [rheumatoid arthritis vs others]). Odds ratios and hazard ratios and their 95% CIs were calculated as effect size, by dividing the two population mean differences by their SD. This study is registered with ClinicalTrials.gov, NCT04353609.Findings: Between April 15, 2020, and Nov 20, 2020, data were collected for 1090 patients (mean age 55·2 years [SD 16·4]); 734 (67%) were female and 356 (33%) were male. Of the 1090 patients, 137 (13%) developed severe COVID-19 and 89 (8%) died. After adjusting for potential confounding factors, severe disease was observed more frequently (effect size 3·26, 95% CI 1·66-6·40, p=0·0006) and the duration of hospital stay was markedly longer (0·62, 0·46-0·85, p=0·0024) in the 63 patients in the rituximab group than in the 1027 patients in the no rituximab group. 13 (21%) of 63 patients in the rituximab group died compared with 76 (7%) of 1027 patients in the no rituximab group, but the adjusted risk of death was not significantly increased in the rituximab group (effect size 1·32, 95% CI 0·55-3·19, p=0·53).Interpretation: Rituximab therapy is associated with more severe COVID-19. Rituximab will have to be prescribed with particular caution in patients with inflammatory rheumatic and musculoskeletal diseases