867 research outputs found
Measurement of the Top Quark Mass with a Matrix Element Method in the Lepton Plus Jets Channel at CDF
We present a measurement of the mass of the top quark from ppbar collisions
at 1.96 TeV observed with the Collider Detector at Fermilab (CDF) at the
Fermilab Tevatron Run II. The events have the decay signature of ppbar to ttbar
in the lepton plus jets channel in which at least one jet is identified as
coming from a secondary vertex and therefore a b-hadron. The largest systematic
uncertainty, the jet energy scale (JES), is convoluted with the statistical
error using an in-situ measurement of the hadronic W boson mass. We calculate a
likelihood for each event using leading-order ttbar and W+jets cross-sections
and parameterized parton showering. The final measured top quark mass and JES
systematic is extracted from a joint likelihood of the product of individual
event likelihoods. From 118 events observed in 680 pb-1 of data, we measure a
top quark mass of 174.09 +- 2.54 (stat+JES) +- 1.35 (syst) GeV/c2.Comment: Proceedings for the 41st Rencontres de Moriond, EWK, March 11 - 28,
2006. 4 pages, 1 figur
Enantioselective Total Synthesis of (+)-Cassiol
An enantioselective total synthesis of (+)-cassiol is reported. The complex derived from Pd-2(pmdba)(3) and enantiopure t-BuPHOX ligand catalyzes enantioconvergent decarboxylative alkylation to generate the quaternary carbon stereocenter at an early stage. The overall synthetic strategy involves a convergent late-stage coupling of two fragments. The synthesis features a longest linear sequence of eight steps
Emergency department hyperoxia is associated with increased mortality in mechanically ventilated patients: A cohort study
Definitions of comorbid conditions. (DOCX 13 kb
Protocol for a multicentre, prospective cohort study of practice patterns and clinical outcomes associated with emergency department sedation for mechanically ventilated patients: The ED-SED Study
Enantioselective Tsuji Allylations
The family of allylation reactions developed by Tsuji in the 1980s are capable of generating tertiary and quaternary carbon stereocenters from several synthetic precursors. Despite the utility of these transformations, they have seen little use in the synthesis of natural products. Recently, the power of these reactions was significantly enhanced by the development of enantioselective versions of these transformations. Applications of these methods to the enantioselective syntheses of natural products and pharmaceutical compounds highlight the importance of these developments
Holistic Hardware Counter Performance Analysis of Parallel Programs
The KOJAK toolkit has been augmented with refined hardware performance counter support, including more convenient measurement specification, additional metric derivations and hierarchical structuring, and an extended algebra for integrating multiple experiments. Comprehensive automated analysis of a hybrid OpenMP/MPI parallel program, the ASC Purple sPPM benchmark, is demonstrated with performance experiments on equisized POWER4-II-based IBM Regatta p690+ cluster, Opteron-based Cray XD1 cluster and UltraSPARC-IV-based Sun Fire E25000 systems. Automatically assessed communication and synchronisation performance properties, combined with a rich set of measured and derived counter metrics, provide a holistic analysis context and facilitate multi-platform comparison
A precise measurement of the top quark mass
We present a measurement of the mass of the top quark using data from proton-antiproton collisions recorded at the CDF experiment in Run II of the Fermilab Tevatron. Events are selected from the single lepton plus jets final state (t{bar t} {yields} W{sup +}bW{sup -}{bar b} {yields} {ell}{nu}bq{bar q}{prime}{bar b}). The top quark mass is extracted using a calculation of the probability density for a t{bar t} final state to resemble a data event. This probability density is a function of both top quark mass and energy scale of calorimeter jets, constrained in situ with the hadronic W boson mass. Using 167 events observed in 955 pb{sup -1} integrated luminosity, we achieve the single most precise measurement of top quark mass to date of 170.8 {+-} 2.2 (stat.) {+-} 1.4 (syst.) GeV/c{sup 2}, where the quoted statistical uncertainty includes uncertainty from the determination of the jet energy scale
Preparation of (S)-2-Allyl-2-methylcyclohexanone (Cyclohexanone, 2-methyl-2-(2-propen-1-yl)-, (2S)-)
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