7,237 research outputs found

    Angular Distribution and CP Asymmetries in the Decays B->K^-pi^+e^-e^+ and B->pi^-pi^+e^-e^+

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    The short-distance Hamiltonian describing b->s(d)e^-e^+ in the standard model is used to obtain the decay spectrum of \bar{B}->K^-pi^+e^-e^+ and \bar{B}->pi^-pi^+e^-e^+, assuming the Kpi and pipi systems to be the decay products of K^* and rho respectively. Specific features calculated are (i) angular distribution of K^- (or pi^-) in the K^-pi^+ (or pi^-pi^+) centre-of-mass (c.m.) frame; (ii) angular distribution of e^- in the e^-e^+ c.m. frame; and (iii) the correlation between the meson and lepton planes. We also derive CP-violating observables obtained by combining the above decays with the conjugate processes B->K^+pi^-e^-e^+ and B->pi^-pi^+e^-e^+.Comment: 19 pages, REVTeX, no figures. Equations (2.19a), (2.19b), (5.5)-(5.7) have been corrected; all results remain unchanged. These changes will appear in an Erratum submitted to Phys. Rev.

    Adiabatic radio frequency potentials for the coherent manipulation of matter waves

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    Adiabatic dressed state potentials are created when magnetic sub-states of trapped atoms are coupled by a radio frequency field. We discuss their theoretical foundations and point out fundamental advantages over potentials purely based on static fields. The enhanced flexibility enables one to implement numerous novel configurations, including double wells, Mach-Zehnder and Sagnac interferometers which even allows for internal state-dependent atom manipulation. These can be realized using simple and highly integrated wire geometries on atom chips.Comment: 13 pages, 2 figure

    Modeling near-field radiative heat transfer from sharp objects using a general 3d numerical scattering technique

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    We examine the non-equilibrium radiative heat transfer between a plate and finite cylinders and cones, making the first accurate theoretical predictions for the total heat transfer and the spatial heat flux profile for three-dimensional compact objects including corners or tips. We find qualitatively different scaling laws for conical shapes at small separations, and in contrast to a flat/slightly-curved object, a sharp cone exhibits a local \emph{minimum} in the spatially resolved heat flux directly below the tip. The method we develop, in which a scattering-theory formulation of thermal transfer is combined with a boundary-element method for computing scattering matrices, can be applied to three-dimensional objects of arbitrary shape.Comment: 5 pages, 4 figures. Corrected background information in the introduction, results and discussion unchange

    Inquiry-based leadership:The influence of affective attitude, experienced social pressure and self-efficacy

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    Purpose The purpose of this paper is to improve the understanding of psychological factors that influence inquiry-based leadership. This study investigates how affective attitude, experienced social pressure, and self-efficacy relate to aspects of inquiry-based school leadership. A school leader’s inquiry habit of mind, data literacy, and the extent to which he or she creates a culture of inquiry in the school are each identified as aspects of inquiry-based leadership. Design/methodology/approach Data were collected from questionnaires completed by a sample of 79 school leaders. Findings A significant relationship was found between self-efficacy regarding inquiry-based leadership and all aspects of inquiry-based leadership. Affective attitude toward inquiry-based leadership was significantly related to creating a culture of inquiry. There was no unique relationship between experienced social pressure and inquiry-based leadership. Practical implications Administrators and educators of school leaders who aim to stimulate inquiry-based school leadership should not only focus on increasing the capacity of school leaders to lead their school in an inquiry-based way, but they should also focus on leaders’ self-efficacy and on fostering leaders’ positive attitude toward inquiry-based school leadership. Administrators and educators can, for example, give positive feedback, emphasize the added value of inquiry-based leadership, encourage working with critical friends, and stimulate collaboration with other leaders. Originality/value This study addresses two gaps in the existing research, by focusing on inquiry-based leadership instead of data use and on psychological factors instead of knowledge and skills that are related to this type of leadership

    Hydrodynamic coupling and rotational mobilities near planar elastic membranes

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    We study theoretically and numerically the coupling and rotational hydrodynamic interactions between spherical particles near a planar elastic membrane that exhibits resistance towards shear and bending. Using a combination of the multipole expansion and Faxen's theorems, we express the frequency-dependent hydrodynamic mobility functions as a power series of the ratio of the particle radius to the distance from the membrane for the self mobilities, and as a power series of the ratio of the radius to the interparticle distance for the pair mobilities. In the quasi-steady limit of zero frequency, we find that the shear- and bending-related contributions to the particle mobilities may have additive or suppressive effects depending on the membrane properties in addition to the geometric configuration of the interacting particles relative to the confining membrane. To elucidate the effect and role of the change of sign observed in the particle self and pair mobilities, we consider an example involving a torque-free doublet of counterrotating particles near an elastic membrane. We find that the induced rotation rate of the doublet around its center of mass may differ in magnitude and direction depending on the membrane shear and bending properties. Near a membrane of only energetic resistance toward shear deformation, such as that of a certain type of elastic capsules, the doublet undergoes rotation of the same sense as observed near a no-slip wall. Near a membrane of only energetic resistance toward bending, such as that of a fluid vesicle, we find a reversed sense of rotation. Our analytical predictions are supplemented and compared with fully resolved boundary integral simulations where a very good agreement is obtained over the whole range of applied frequencies.Comment: 14 pages, 7 figures. Revised manuscript resubmitted to J. Chem. Phy

    CP Violation in the Decay B \to X_d e^+ e^-

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    The decay bde+eb\to d e^+e^- has an amplitude containing comparable contributions proportional to VtbVtdV_{tb}V_{td}^{*}, VcbVcdV_{cb}V_{cd}^{*} and VubVudV_{ub}V_{ud}^{*}. These pieces involve different unitarity phases produced by ccˉc\bar{c} and uuˉu\bar{u} loops. The simultaneous presence of different CKM phases and different dynamical phases leads to a calculable asymmetry in the partial widths of bde+eb\to d e^+e^- and bˉdˉe+e\bar{b}\to \bar{d} e^+e^-. Using the effective Hamiltonian of the standard model, we calculate this asymmetry as a function of the e+ee^+e^- invariant mass. The effects of ρ\rho, ω\omega and J/ψJ/\psi resonances are taken into account in the vacuum polarization of the uuˉu\bar{u} and ccˉc\bar{c} currents. As a typical result, an asymmetry of 5(2- 5% (- 2%) is predicted in the nonresonant domain 1GeV<me+e<mJ/ψ1 GeV < m_{e^+e^-} < m_{J/\psi}, assuming η=0.34\eta = 0.34 and ρ=0.3(0.3)\rho= 0.3 (-0.3). The branching ratio in this domain is 1.2×107(3.3×107)1.2\times 10^{-7} (3.3\times 10^{-7}). Results are also obtained in the region of the J/ψJ/\psi resonance, where an asymmetry of 3×1033\times 10^{-3} is expected, subject to certain theoretical uncertainties in the bdJ/ψb\to d J/\psi amplitude.Comment: 20 pages, LaTeX, 3 eps figures, uses cite.sty, epsf.sty, and amssym.sty. Version to appear in Phys. Rev. D, with some minor addition

    Status of a DEPFET pixel system for the ILC vertex detector

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    We have developed a prototype system for the ILC vertex detector based on DEPFET pixels. The system operates a 128x64 matrix (with ~35x25 square micron large pixels) and uses two dedicated microchips, the SWITCHER II chip for matrix steering and the CURO II chip for readout. The system development has been driven by the final ILC requirements which above all demand a detector thinned to 50 micron and a row wise read out with line rates of 20MHz and more. The targeted noise performance for the DEPFET technology is in the range of ENC=100 e-. The functionality of the system has been demonstrated using different radioactive sources in an energy range from 6 to 40keV. In recent test beam experiments using 6GeV electrons, a signal-to-noise ratio of S/N~120 has been achieved with present sensors being 450 micron thick. For improved DEPFET systems using 50 micron thin sensors in future, a signal-to-noise of 40 is expected.Comment: Invited poster at the International Symposium on the Development of Detectors for Particle, AstroParticle and Synchrotron Radiation Experiments, Stanford CA (SNIC06) 6 pages, 12 eps figure
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