8,107 research outputs found

    Form Factors for Exclusive Semileptonic BB--Decays

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    We developed the new parton model approach for exclusive semileptonic decays of BB-meson to D, DD,~D^* by extending the inclusive parton model, and by combining with the results of the HQET, motivated by Drell-Yan process. Without the nearest pole dominance ans\"atze, we {\bf derived} the dependences of hadronic form factors on q2q^2. We also calculated numerically the slope of the Isgur-Wise function, which is consistent with the experimental results.Comment: 20 pages, RevTex, 2 ps figure files(uuencoded in seperate file

    Heisenberg-picture approach to the exact quantum motion of a time-dependent forced harmonic oscillator

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    In the Heisenberg picture, the generalized invariant and exact quantum motions are found for a time-dependent forced harmonic oscillator. We find the eigenstate and the coherent state of the invariant and show that the dispersions of these quantum states do not depend on the external force. Our formalism is applied to several interesting cases.Comment: 15 pages, two eps files, to appear in Phys. Rev. A 53 (6) (1996

    Remarks on the Upper Bounds on the Higgs Boson Mass from Triviality

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    We study the effects of the one-loop matching conditions on Higgs boson and top quark masses on the triviality bounds on the Higgs boson mass using βλ\beta_{\lambda} with corrected two-loop coefficients. We obtain quite higher results than previous ones and observe that the triviality bounds are not nearly influenced by varying top quark mass over the range measured at CDF and D0. The effects of typo errors in βλ(2)\beta_{\lambda}^{(2)} and the one-loop matching condition on the top quark mass are negligible. We estimate the size of effects on the triviality bounds from the one-loop matching condition on the Higgs boson mass.Comment: 9 pages, tar'ed gzip'ed uuencoded files, LaTex, 5 PostScript figures. To appear in Physical Review

    Effects of metallic spacer in layered superconducting Sr2(Mgy_yTi1y_{1-y})O3FeAs

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    The highly two-dimensional superconducting system Sr2(Mgy_yTi1y_{1-y})O3FeAs, recently synthesized in the range of 0.2 < y < 0.5, shows an Mg concentration-dependent TcT_c. Reducing the Mg concentration from y=0.5 leads to a sudden increase in TcT_c, with a maximum TcT_c ~40 K at y=0.2. Using first principles calculations, the unsynthesized stoichiometric y=0 and the substoichiometric y=0.5 compounds have been investigated. For the 50% Mg-doped phase (y=0.5), Sr2(Mgy_yTi1y_{1-y})O3 layers are completely insulating spacers between FeAs layers, leading to the fermiology such as that found for other Fe pnictides. At y=0, representing a phase with metallic Sr2TiO3 layers, the Γ\Gamma-centered Fe-derived Fermi surfaces (FSs) considerably shrink or disappear. Instead, three Γ\Gamma-centered Ti FSs appear, and in particular two of them have similar size, like in MgB2. Interestingly, FSs have very low Fermi velocity in large fractions: the lowest being 0.6×106\times10^6 cm/s. Furthermore, our fixed spin moment calculations suggest the possibility of magnetic ordering, with magnetic Ti and nearly nonmagnetic Fe ions. These results indicate a crucial role of Sr2(Mgy_yTi1y_{1-y})O3 layers in this superconductivity.Comment: 7 pages; Proceedings of ICSM-201

    First year of 24/7 Acute Stroke Unit. Part 2: outcome of stroke thrombolysis using telemedicine

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    OBJECTIVE: To evaluate the safety and efficacy of intravenous recombinant tissue plasminogen activator (IV-rtPA) for acute ischaemic stroke through telemedicine consultation …published_or_final_versio

    First year of 24/7 Acute Stroke Unit. Part 1: eligibility and utilisation of intravenous thrombolysis

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    INTRODUCTION: Intravenous recombinant tissue plasminogen activator (IV-rtPA) is the standard therapy for acute ischaemic stroke. Because of its narrow therapeutic time window, eligibility and utilisation rates of this treatment remained low. Our IV-rtPA programme was enhanced to a 24/7 protocol since September 20…published_or_final_versio

    Study protocol for a randomised controlled trial of invasive versus conservative management of primary spontaneous pneumothorax

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    INTRODUCTION: Current management of primary spontaneous pneumothorax (PSP) is variable, with little evidence from randomised controlled trials to guide treatment. Guidelines emphasise intervention in many patients, which involves chest drain insertion, hospital admission and occasionally surgery. However, there is evidence that conservative management may be effective and safe, and it may also reduce the risk of recurrence. Significant questions remain regarding the optimal initial approach to the management of PSP

    Constraints on the R-parity- and Lepton-Flavor-Violating Couplings from B0 Decats to Two Charged Leptons

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    We derive the upper bounds on certain products of R-parity- and lepton-flavor-violating couplings from the decays of the neutral BB meson into two charged leptons. These modes of B0B^0 decays can constrain the product combinations of the couplings with one or more heavy generation indices. We find that most of these bounds are stronger than the previous ones.Comment: Table is changed; version to appear in Phys. Rev.
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