2,004 research outputs found

    Tracker Alignment Strategy in CMS and Experience with Cosmic Ray Data

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    Aligning the CMS silicon tracker is an unprecedented challenge due to the more than 15~000 modules that it is composed of. Besides high precision mounting, survey measurements and the laser alignment system, track based alignment is needed to reach the envisaged precision. The first successful full scale alignment study on simulated data uses a fast global minimisation procedure implemented in the Millepede~II program. Tracks from cosmic ray muons and the inclusion of prior knowledge are key ingredients. Experience beyond simulation studies is gained analysing real data from cosmic ray muons

    A Study of Full Scale CMS Tracker Alignment using High Momentum Muons and Cosmics

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    The positions of the silicon modules of the CMS tracker will be known to O(100O(100 μ\mum) from survey measurements, mounting precision and the laser alignment system. However, in order to fully exploit the capabilities of the tracker, these positions need to be known to a precision of a few μ\mum. Only a track-based alignment procedure can reach this required precision. Such an alignment procedure is a major challenge given that about 50000 geometry constants need to be measured. Making use of the novel χ2\chi^2 minimization program Millepede II an alignment strategy has been developed in which all detector components are aligned simultaneously and all correlations between their position parameters taken into account. Different datasets, such as Z0^0 decays and cosmic muons, plus information about the mechanical structure of the tracker, and initial position uncertainties have been used as input for the alignment procedure. A proof of concept of this alignment strategy is demonstrated using simulated data

    The Term Structure of Expected Inflation Based on Bond and TIPS

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    预期通货膨胀期限结构(thetermstructureofexpectedinflation)指具有相同风险及流动性的债券,其预期通货膨胀率变化随到期日的时间长短不同而产生不同的结构。它是一个国家宏观经济政策运行效率的基准之一,同时也是一个国家获取市场对未来通货膨胀预期信息的重要手段。相对于利率的期限结构,预期通货膨胀期限结构更为复杂。本文旨在构建预期通货膨胀期限结构动态模型,即将预期通货膨胀作为一个直接的主要影响因素,运用套利定价理论的方法,构建预期通货膨胀期限结构模型。首先,基于一般债券的预期通货膨胀期限结构动态模型是在回顾了国外相关模型的基础上,利用套利定价理论和Merton的连续时间研...For the past last 30 years, tremendous progress has been made in modeling the dynamics of the term structure of interest rates and expected inflation, which plays an instrumental role in determining prices and hedging portfolios of fixed-income derivative securities. The term structure of expected inflation is a key to assessing the credibility of fiscal and monetary policies, to examining how bor...学位:经济学博士院系专业:经济学院金融系_金融学(含保险学)学号:B20011203

    The Impact of Age on Outcome of Embryonal and Alveolar Rhabdomyosarcoma Patients.:A Multicenter Study

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    Background: The prognosis of rhabdomyosarcoma (RMS) in children and adolescents has improved since the introduction of multi-agent chemotherapy. However, outcome data of adults with RMS are scarce. This multicenter retrospective study investigated the effect of age on outcome of RMS. Patients and Methods: Data were collected from three Dutch University Medical Centers between 1977-2009. The effect of age and clinical prognostic factors on relapse-free and disease-specific survival (DSS) were analyzed. Results: Age as a continuous variable predicted poor survival in multivariate analysis. Five-year DSS was highest for non-metastatic embryonal RMS, followed by non-metastatic alveolar RMS and was poor in metastatic disease. Higher age correlated with unfavorable histological subtype (alveolar RMS) and with metastatic disease at presentation in embryonal RMS. In non-metastatic embryonal RMS and in all alveolar RMS, higher age was an adverse prognostic factor of outcome. Conclusion: This study indicates that age is a negative predictor of survival in patients with embryonal and alveolar RMS

    Search for Doubly-Charged Higgs Boson Production at HERA

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    A search for the single production of doubly-charged Higgs bosons H^{\pm \pm} in ep collisions is presented. The signal is searched for via the Higgs decays into a high mass pair of same charge leptons, one of them being an electron. The analysis uses up to 118 pb^{-1} of ep data collected by the H1 experiment at HERA. No evidence for doubly-charged Higgs production is observed and mass dependent upper limits are derived on the Yukawa couplings h_{el} of the Higgs boson to an electron-lepton pair. Assuming that the doubly-charged Higgs only decays into an electron and a muon via a coupling of electromagnetic strength h_{e \mu} = \sqrt{4 \pi \alpha_{em}} = 0.3, a lower limit of 141 GeV on the H^{\pm\pm} mass is obtained at the 95% confidence level. For a doubly-charged Higgs decaying only into an electron and a tau and a coupling h_{e\tau} = 0.3, masses below 112 GeV are ruled out.Comment: 15 pages, 3 figures, 1 tabl

    Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA

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    Deep-inelastic positron-proton interactions at low values of Bjorken-x down to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons are studied with the H1 experiment at HERA. The inclusive cross section for pi^0 mesons produced at small angles with respect to the proton remnant (the forward region) is presented as a function of the transverse momentum and energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x. Measurements are also presented of the transverse energy flow in events containing a forward pi^0 meson. Hadronic final state calculations based on QCD models implementing different parton evolution schemes are confronted with the data.Comment: 27 pages, 8 figures and 3 table

    Measurements of branching fraction ratios and CP-asymmetries in suppressed B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^- decays

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    We report the first reconstruction in hadron collisions of the suppressed decays B^- -> D(-> K^+ pi^-)K^- and B^- -> D(-> K^+ pi^-)pi^-, sensitive to the CKM phase gamma, using data from 7 fb^-1 of integrated luminosity collected by the CDF II detector at the Tevatron collider. We reconstruct a signal for the B^- -> D(-> K^+ pi^-)K^- suppressed mode with a significance of 3.2 standard deviations, and measure the ratios of the suppressed to favored branching fractions R(K) = [22.0 \pm 8.6(stat)\pm 2.6(syst)]\times 10^-3, R^+(K) = [42.6\pm 13.7(stat)\pm 2.8(syst)]\times 10^-3, R^-(K)= [3.8\pm 10.3(stat)\pm 2.7(syst]\times 10^-3, as well as the direct CP-violating asymmetry A(K) = -0.82\pm 0.44(stat)\pm 0.09(syst) of this mode. Corresponding quantities for B^- -> D(-> K^+ pi^-)pi^- decay are also reported.Comment: 8 pages, 1 figure, accepted by Phys.Rev.D Rapid Communications for Publicatio

    Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

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    The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO
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