1,779 research outputs found

    The Concurrent Track Evolution Algorithm: Extension for Track Finding in the Inhomogeneous Magnetic Field of the HERA-B Spectrometer

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    The Concurrent Track Evolution method, which was introduced in a previous paper (DESY 97-054), has been further explored by applying it to the propagation of track candidates into an inhomogeneous magnetic field volume equipped with tracking detectors, as is typical for forward B spectrometers like HERA-B or LHCb. Compared to the field-free case, the method was extended to three-dimensional propagation, with special measures necessary to achieve fast transport in the presence of a fast-varying magnetic field. The performance of the method is tested on HERA-B Monte Carlo events with full detector simulation and a realistic spectrometer geometry.Comment: 26 pages (Latex), 11 figures (Postscript

    Summary of the Heavy Flavor Working Group

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    During the last year many important results have been achieved in heavy flavour physics: New measurements of charm and beauty production have been performed at HERA and the Tevatron. A wealth of new spectroscopy data with several new, unexpected states in the charmonium and the D_s systems has been collected and b to d gamma transitions have been established. The oscillation frequency in the B_s Bbar_s is now measured, and mixing in the D0 D0bar system has been observed. Theoretical progress in the areas of open heavy flavour production, quarkonium production and decays, and multiquark spectroscopy has been presented at this workshop.Comment: 17 pages, 3 figures, to appear in the Proceedings of the XV International Workshop on Deep-Inelastic Scattering and Related Subjectes, DIS 2007, April 16--20, 2007, Munich, German

    n-type doping of organic semiconductors : immobilization via covalent anchoring

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    We gratefully acknowledge the German Federal Ministry of Education and Research (BMBF) for financial support within the InterPhase project (FKZ 13N13659, 13N13656, 13N13657, and 13N13658).Electrical doping is an important tool in the design of organic devices to modify charge carrier concentration in and Fermi level position of organic layers. The undesired diffusion of dopant molecules within common transport materials adversely affects both lifetime and device performance. To overcome this drawback, we developed a strategy to achieve immobilization of dopants through their covalent attachment to the semiconductor host molecules. Derivatization of the commonly employed n-type dopant 2-(2-methoxyphenyl)-1,3-dimethyl-2,3-dihydro-1H-benzoimidazole (őŅ-MeO-DMBI) with a phenylazide enables the resulting o-AzBnO-DMBI to photochemically generate a reactive nitrene, which subsequently binds covalently to the host material, 6,6-phenyl-C61-butyric acid methyl ester (PCBM). Both the activation and addition reactions are monitored by mass spectrometry as well as optical and photoelectron spectroscopy. A suppression of desorption and a decrease in volatility of the DMBI derivative in ultrahigh vacuum were observed after activation of a bilayer structure of PCBM and o-AzBnO-DMBI. Electrical measurements demonstrate that the immobilized o-AzBnO-DMBI can (i) dope the PCBM at conductivities comparable to values reported for o-MeO-DMBI in the literature and (ii) yield improved electrical stability measured in a lateral two terminal device geometry. Our immobilization strategy is not limited to the specific system presented herein but should also be applicable to other organic semiconductor‚Äďdopant combinations.Publisher PDFPeer reviewe

    Differential cross section measurements for the production of a W boson in association with jets in proton‚Äďproton collisions at ‚ąös = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript ‚ąí1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

    Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an