1,420 research outputs found

    Top quark pair production and top quark properties at CDF

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    We present the most recent measurements of top quark pairs production and top quark properties in proton-antiproton collisions with center-of-mass energy of 1.96 TeV using CDF II detector at the Tevatron. The combination of top pair production cross section measurements and the direct measurement of top quark width are reported. The test of Standard Model predictions for top quark decaying into bb-quarks, performed by measuring the ratio RR between the top quark branching fraction to bb-quark and the branching fraction to any type of down quark is shown. The extraction of the CKM matrix element Vtb|V_{tb}| from the ratio RR is discussed. We also present the latest measurements on the forward-backward asymmetry (AFBA_{FB}) in top anti-top quark production. With the full CDF Run II data set, the measurements are performed in top anti-top decaying to final states that contain one or two charged leptons (electrons or muons). In addition, we combine the results of the leptonic forward-backward asymmetry in ttˉt\bar t system between the two final states. All the results show deviations from the next-to-leading order (NLO) standard model (SM) calculation.Comment: 6 pages, 5 figures, Contribution to the proceedings of 37th International Conference on High Energy Physics (ICHEP) in Valencia, Spain, July 2-9 201

    Top Physics at CDF

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    We present the recent results of top-quark physics using up to 6 fb1^{-1} of ppˉp \bar p collisions at a center of mass energy of s\sqrt s = 1.96 TeV analyzed by the CDF collaboration. Thanks to this large data sample, precision top quark measurements are now a reality at the Tevatron. Further, several new physics signals could appear in this large dataset. We will present the latest measurements of top quark intrinsic properties as well as direct searches for new physics in the top sector.Comment: Contribution to the proceedings of XIX International Workshop on Deep-Inelastic Scattering and Related Subjects (DIS 2011), 4 page

    Production of single top quark - results from the Tevatron and the LHC

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    We present the most recent measurements of single top quark production cross section by the CDF and D0 experiments at the Fermilab Tevatron Collider and the ATLAS and CMS experiments at the Large Hadron Collider (LHC). The data were collected at the Tevatron corresponding to an integrated luminosity of up to 9.7 fb1^{-1} of proton-antiproton (ppˉp\bar p) collisions at a centre-of-mass energy of 1.96 TeV and at the LHC corresponding to an integrated luminosity of up to 4.9 fb1^{-1} of proton-proton (pppp) collisions at a centre-of-mass energy of 7 TeV in 2011 and up to 20.3 fb1^{-1} at a centre-of-mass energy of 8 TeV in 2012. The measurements of single top quark production in ss-channel, tt-channel and associated production of a top quark and a WW-boson (tWtW production) are presented separately and lower limits on the CKM matrix element Vtb|V_{tb}| from the single top quark cross section are set.Comment: 5 pages, 4 figures, for the ATLAS, CDF, CMS and D0 collaborations, Presented at 26th Rencontres de Blois, Particle Physics and Cosmology, May 18-23, 201

    Pixel data real time processing as a next step for HL-LHC upgrades and beyond

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    The experiments at LHC are implementing novel and challenging detector upgrades for the High Luminosity LHC, among which the tracking systems. This paper reports on performance studies, illustrated by an electron trigger, using a simplified pixel tracker. To achieve a real-time trigger (e.g. processing HL-LHC collision events at 40 MHz), simple algorithms are developed for reconstructing pixel-based tracks and track isolation, utilizing look-up tables based on pixel detector information. Significant gains in electron trigger performance are seen when pixel detector information is included. In particular, a rate reduction up to a factor of 20 is obtained with a signal selection efficiency of more than 95\% over the whole η\eta coverage of this detector. Furthermore, it reconstructs p-p collision points in the beam axis (z) direction, with a high precision of 20 μ\mum resolution in the very central region (η<0.8|\eta| < 0.8), and, up to 380 μ\mum in the forward region (2.7 <η<< |\eta| < 3.0). This study as well as the results can easily be adapted to the muon case and to the different tracking systems at LHC and other machines beyond the HL-LHC. The feasibility of such a real-time processing of the pixel information is mainly constrained by the Level-1 trigger latency of the experiment. How this might be overcome by the Front-End ASIC design, new processors and embedded Artificial Intelligence algorithms is briefly tackled as well.Comment: To be submitted to JHE

    Development of functional gastrointestinal disorder symptoms following laparoscopic cholecystectomy: a prospective cohort study

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    BackgroundThe casual relationship between the role of cholecystectomy and functional gastrointestinal disorders (FGIDs) are a controversial clinical challenge. This study aimed to investigate: (1) the overlap of FGIDs before cholecystectomy and its long-term outcome after surgery in patients with symptomatic cholelithiasis, and (2) the incidence of new-onset FGIDs after cholecystectomy.MethodsPatients with symptomatic gallstone disease who underwent elective, laparoscopic cholecystectomy were prospectively enrolled. Healthy populations who underwent medical check-ups were selected as age- and sex-matched controls. Questionnaires regarding sociodemographic characteristics, gastrointestinal symptoms and a somatization symptom checklist (SSC) were completed at baseline and 12 months thereafter.ResultsThe prevalence of all FGID symptoms before cholecystectomy were significantly higher in the group of patients with symptomatic cholecystolithiasis compared to the control group. In cholecystectomy group, the preoperative FGID symptoms improved after surgery, except for chronic diarrhea. Compared to the controls, the new-onset FGIDs, including functional dyspepsia (14.8% vs. 6.9%; p = 0.040), functional diarrhea (6.6% vs. 0.2%; p &lt; 0.001), and chronic abdominal pain (11.9% vs. 4.4%; p = 0.024), were more common at 1 year after cholecystectomy. Somatization was independent predictors of new-onset dyspepsia and abdominal pain, while newly occurring diarrhea was not realted to somatization.ConclusionOverlap of FGIDs was common in patients with symptomatic cholelithiasis before surgery and at follow-up 1 year after cholecystectomy. Furthermore, new-onset FGIDs could be occurred after cholecystectomy. Therefore, a delicate diagnostic approaches and appropriate treatments about co-existent FGIDs should be given in patients with cholelithiasis before and after cholecystectomy

    Report of a Korean Patient with Cystic Fibrosis, Carrying Q98R and Q220X Mutations in the CFTR Gene

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    Although cystic fibrosis (CF) is one of the most frequently seen autosomal-recessive disorders in Caucasians, it is extremely rare in the Korean population. Recently, a 15-yr-old Korean boy was admitted to our hospital complaining of coughing, sputum, and exertional dyspnea. Chest radiographs and computed tomographic chest and paranasal sinus scans revealed diffuse bronchiectasis and pansinusitis. Pulmonary function tests revealed severe obstructive impairment. The average sweat chloride concentrations on both of the patients' forearms were 63.0 mM/L (reference limit: <40 mM/L). Upon mutation analysis, two different mutations (Q98R and Q220X) were identified in the cystic fibrosis transmembrane conductance regulator gene, both of which had been previously detected in CF patients, one from France and the other from England. As CF is quite rare in Korea, the diagnosis of CF in this patient might be delayed. Therefore, we recommend that a diagnosis of CF should be suspected in patients exhibiting unexplained chronic respiratory symptoms