We present a precision measurement of the top-quark mass using the full sample of Tevatron √s = 1.96 TeV proton-antiproton collisions collected by the CDF II detector, corresponding to an integrated ...luminosity of 8.7 fb(-1). Using a sample of tt¯ candidate events decaying into the lepton+jets channel, we obtain distributions of the top-quark masses and the invariant mass of two jets from the W boson decays from data. We then compare these distributions to templates derived from signal and background samples to extract the top-quark mass and the energy scale of the calorimeter jets with in situ calibration. The likelihood fit of the templates from signal and background events to the data yields the single most-precise measurement of the top-quark mass, M(top)=172.85±0.71(stat)±0.85(syst) GeV/c(2).
We present a combination of searches for the standard model Higgs boson using the full CDF run II data set, which corresponds to an integrated luminosity of 9.45-10.0 fb super(-1) collected from ...radicals = 1.96 TeV pp collisions at the Fermilab Tevatron. The searches consider Higgs boson production from gluon-gluon fusion, vector-boson fusion, and associated production with either a W or Z boson or a tt pair. Depending on the production mode, Higgs boson decays to W super(+)W super(-), ZZ, bb, tau super(+)tau super(-), and gamma gamma are examined. We search for a Higgs boson with masses (m sub(H)) in the range 90-200 GeV /c super(2). In the absence of a signal, we expect based on combined search sensitivity to exclude at the 95% credibility level the mass regions 90 < m sub(H) < 94 GeV /c super(2), 96 < m sub(H) < 106 GeV /c super(2), and 153 < m sub(H) < 175 GeV /c super(2). The observed exclusion regions are 90 < m sub(H) < 102 GeV /c super(2) and 149 < m sub(H) < 172 GeV /c super(2). A moderate excess of signal-like events relative to the background expectation at the level of 2.0 standard deviations is present in the data for the m sub(H) = 125 GeV /c super(2) search hypothesis. We also present interpretations of the data within the context of a fermiophobic model and an alternative standard model incorporating a fourth generation of fermions. Finally, for the hypothesis of a new particle with mass 125 GeV /c super(2), we constrain the coupling strengths of the new particle to W super(+ or -) bosons, Z bosons, and fermions.
Due to the limitation in treatment window of the rtPA (recombinant tissue plasminogen activator), the development of delayed treatment for stroke is needed. We previously reported that there is a ...difference in neurogenesis and neuroblast migration patterns in different mouse stroke models (proximal and distal middle cerebral artery occlusion models, pMCAo or dMCAo). Specifically, compared to robust neurogenesis and substantial migration of newly born neuroblasts in pMCAo model, dMCAo only illicit limited neurogenesis and migration of neuroblasts towards ischemic area. One potential reason for this difference is the relative location of ischemic area to white matter and the neurogenic niche (subventricular zone, SVZ). Specifically, white matter could serve as a physical barrier or inhibitory factor to neurogenesis and migration in the dMCAo model. Given that a major difference in human and rodent brains is the content of white matter in the brain, in this study, we further characterize these two models and test the important hypothesis that white matter is an important contributing inhibitory factor for the limited neurogenesis in the dMCAo model. We utilized a genetically inducible NSC-specific reporter mouse line (nestin-CreERT2-R26R-YFP) to label and track NSC proliferation, survival and differentiation in ischemic brain. To test whether myelin is inhibitory to neurogenesis in dMCAo model, we demyelinated mouse brains using cuprizone treatment after stroke and examined whether there is enhanced neurogenesis or migration of neuroblasts cells in stroke mice treated with cuprizone. Our data suggests that demyelination of the brain does not result in enhanced neurogenesis or migration of neuroblasts, supporting that myelin is not a major inhibitory factor for stroke-induced neurogenesis. In addition, our results suggest that in non-stroke mice, demyelination causes decreased neurogenesis in adult brain, indicating a potential positive role of myelin in maintenance of adult neural stem cell niche.
We present the first observation of exclusive e(+)e(-) production in hadron-hadron collisions, using ppover collision data at (square root) s = 1.96 TeV taken by the run II Collider Detector at ...Fermilab, and corresponding to an integrated luminosity of 532 pb(-1). We require the absence of any particle signatures in the detector except for an electron and a positron candidate, each with transverse energy E(T) > 5 GeV and pseudorapidity |eta| < 2. With these criteria, 16 events are observed compared to a background expectation of 1.9+/-0.3 events. These events are consistent in cross section and properties with the QED process ppover --> p + e(+)e(-) + pover through two-photon exchange. The measured cross section is 1.6(-0.3)(+0.5)(stat) +/- 0.3(syst) pb. This agrees with the theoretical prediction of 1.71+/-0.01 pb.
An extensive collection of in-situ snow measurements is used to characterize snow conditions in the entire elevation range of the alpine area of Tyrol, Austria. Regularly observed snow station data ...are evaluated with respect to mean snow density-time curves of the period 1952-2010. Dependent on the observed snow depth (HS), the snow bulk density ( rho ) is statistically modelled for different elevation zones and snow-climate regions. Model improvements allow daily estimates of rho , and introducing an additional parameter accounting for the decrease of bulk density in relation to new snow data further improved the results. This paper describes the development of an additional model for the glacierized sub-region of the Tyrolean Alps, based on snow course data from the peak snow accumulation period in April/May. The resulting relative errors of the different models range from 13 to 25% for single stations distributed over the entire investigation area and from 5 to 20% for annual snow courses in glacierized catchments. Regression models are most accurate at high elevations and for deep snowpacks. The transferability of the presented models is shown between Austria, Switzerland and Italy.
The top-quark mass M sub(top) is measured using top quark-antiquark pairs produced in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV and that decay into a fully hadronic final ...state. The full data set collected with the CDF II detector at the Fermilab Tevatron Collider, corresponding to an integrated luminosity of 9.3 fb super(-1), is used. Events are selected that have six to eight jets, at least one of which is identified as having originated from a b quark. In addition, a multivariate algorithm, containing multiple kinematic variables as inputs, is used to discriminate signal events from background events due to QCD multijet production. Templates for the reconstructed top-quark mass are combined in a likelihood fit to measure M sub(top) with a simultaneous calibration of the jet energy scale. A value of M sub(top) = 175.07 + or - 1.19(stat) (ProQuest: Formulae and/or non-USASCII text omitted)(syst) GeV /c super(2) is obtained for the top-quark mass.
We search for new charmless decays of neutral b hadrons to pairs of charged hadrons, using 1 fb(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We report the first observation ...of the Bs0-->K-pi+ decay and measure B(Bs0-->K-pi+)=(5.0+/-0.7(stat)+/-0.8(syst))x10(-6). We also report the first observation of charmless b-baryon decays, and measure B(Lambdab0-->ppi-)=(3.5+/-0.6(stat)+/-0.9(syst))x10(-6) and B(Lambdab0-->pK-)=(5.6+/-0.8(stat)+/-1.5(syst))x10(-6). No evidence is found for other modes, and we set the limit B(Bs0-->pi+pi;-)<1.2x10(-6) at 90% C.L.
We present an analysis of top-antitop quark production and decay into a tau lepton, tau neutrino, and bottom quark using data from 9 fb super(-1) of integrated luminosity at the Collider Detector at ...Fermilab. Dilepton events, where one lepton is an energetic electron or muon and the other a hadronically decaying tau lepton, originating from proton-antiproton collisions at radicals = 1.96 TeV, are used. A top-antitop quark production cross section of 8.1 + or - 2.1 pb is measured, assuming standard-model top quark decays. By separately identifying for the first time the single-tau and the ditau components, we measure the branching fraction of the top quark into the tau lepton, tau neutrino, and bottom quark to be (9.6 + or - 2.8)%. The branching fraction of top quark decays into a charged Higgs boson and a bottom quark, which would imply violation of lepton universality, is limited to be less than 5.9% at a 95% confidence level for Bernoulli(H super(-) arrow right taunu) = 1.
This Letter reports a search for a narrow resonant state decaying into two W bosons and two b quarks where one W boson decays leptonically and the other decays into a quark-antiquark pair. The search ...is particularly sensitive to top-antitop resonant production. We use the full data sample of proton-antiproton collisions at a center-of-mass energy of 1.96 TeV collected by the CDF II detector at the Fermilab Tevatron, corresponding to an integrated luminosity of 9.45 fb(-1). No evidence for resonant production is found, and upper limits on the production cross section times branching ratio for a narrow resonant state are extracted. Within a specific benchmark model, we exclude a Z' boson with mass, M(Z'), below 915 GeV/c(2) decaying into a top-antitop pair at the 95% credibility level assuming a Z' boson decay width of Γ(Z') = 0.012 M(Z'). This is the most sensitive search for a narrow qq-initiated tt resonance in the mass region below 750 GeV/c(2).
We report a measurement of the single-top-quark production cross section in 2.2 fb;{-1} of pp collision data collected by the Collider Detector at Fermilab at sqrts=1.96 TeV. Candidate events are ...classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of 2.2(-0.6)(+0.7)(stat+syst) pb, extract the Cabibbo-Kobayashi-Maskawa matrix-element value |V(tb)|=0.88(-0.12)(+0.13)(stat+syst)+/-0.07(theory), and set the limit |V(tb)|>0.66 at the 95% C.L.
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