4,452 research outputs found

    Recent results on the Higgs boson searches in the γγ and Zγ decay channels with the ATLAS detector

    Get PDF
    In this paper the latest results on the search for a Higgs boson decaying into photon pairs and Zγ with the ATLAS detector are reviewd. The presented measurements are based on 4.8 fb−1 of integrated luminsity collected in 2011 at a center of mass energy of 7TeV and 20.7 fb−1 collected in 2012 at a center of mass energy of 8TeV

    Rayleigh scattering and atomic dynamics in dissipative optical lattices

    Get PDF
    We investigate Rayleigh scattering in dissipative optical lattices. In particular, following recent proposals [S. Guibal et al., Phys. Rev. Lett. 78, 4709 (1997); C. Jurczak et al., Phys. Rev. Lett. 77, 1727 (1996)], we study whether the Rayleigh resonance originates from the diffraction on a density grating and is therefore a probe of transport of atoms in optical lattices. It turns out that this is not the case: the Rayleigh line is instead a measure of the cooling rate, while spatial diffusion contributes to the scattering spectrum with a much broader resonance

    Calibration of the ATLAS electromagnetic calorimeter using calibration hits

    Get PDF
    In the present note a method to determine the electron energy from the energies measured in an electron cluster is discussed. The method is based on a detailed Monte-Carlo simulation (labeled \textit{Calibration Hits}) of electrons in the ATLAS detector in which also the energies deposited in the passive and dead materials are recorded. It allows also to compute the different contributions (energy deposited in front, in and behind the Accordion) to the total electron energy. To better understand the various contributions to the energy reconstruction three rounds of simulations have been performed: electrons hitting the middle cell centre, electrons spread uniformly over a cell in absence of magnetic field and electrons spread uniformly over a cell in presence of magnetic field. The method is applied to the Barrel calorimeter and to electrons. Its extension to the End Caps and to photons does not pose problems. In the operative ATLAS conditions an energy resolution sampling term varying from 9.9%\% at η\eta=0.3 and 16.8%\% at η\eta=1.2 is obtained. The linearity varies between 0.1%\% and 0.4%\% in the energy interval 10-100GeV over the same η\eta range

    Cold atom realizations of Brownian motors

    Full text link
    Brownian motors are devices which "rectify" Brownian motion, i.e. they can generate a current of particles out of unbiased fluctuations. Brownian motors are important for the understanding of molecular motors, and are also promising for the realization of new nanolelectronic devices. Among the different systems that can be used to study Brownian motors, cold atoms in optical lattices are quite an unusual one: there is no thermal bath and both the potential and the fluctuations are determined by laser fields. In this article recent experimental implementations of Brownian motors using cold atoms in optical lattices are reviewed

    Microtubules Orient the Mitotic Spindle in Yeast through Dynein-dependent Interactions with the Cell Cortex

    Get PDF
    Proper orientation of the mitotic spindle is critical for successful cell division in budding yeast. To investigate the mechanism of spindle orientation, we used a green fluorescent protein (GFP)–tubulin fusion protein to observe microtubules in living yeast cells. GFP–tubulin is incorporated into microtubules, allowing visualization of both cytoplasmic and spindle microtubules, and does not interfere with normal microtubule function. Microtubules in yeast cells exhibit dynamic instability, although they grow and shrink more slowly than microtubules in animal cells. The dynamic properties of yeast microtubules are modulated during the cell cycle. The behavior of cytoplasmic microtubules revealed distinct interactions with the cell cortex that result in associated spindle movement and orientation. Dynein-mutant cells had defects in these cortical interactions, resulting in misoriented spindles. In addition, microtubule dynamics were altered in the absence of dynein. These results indicate that microtubules and dynein interact to produce dynamic cortical interactions, and that these interactions result in the force driving spindle orientation

    Natural extensions and entropy of α\alpha-continued fractions

    Full text link
    We construct a natural extension for each of Nakada's α\alpha-continued fractions and show the continuity as a function of α\alpha of both the entropy and the measure of the natural extension domain with respect to the density function (1+xy)2(1+xy)^{-2}. In particular, we show that, for all 0<α10 < \alpha \le 1, the product of the entropy with the measure of the domain equals π2/6\pi^2/6. As a key step, we give the explicit relationship between the α\alpha-expansion of α1\alpha-1 and of α\alpha

    Cross sections for geodesic flows and \alpha-continued fractions

    Full text link
    We adjust Arnoux's coding, in terms of regular continued fractions, of the geodesic flow on the modular surface to give a cross section on which the return map is a double cover of the natural extension for the \alpha-continued fractions, for each α\alpha in (0,1]. The argument is sufficiently robust to apply to the Rosen continued fractions and their recently introduced \alpha-variants.Comment: 20 pages, 2 figure

    Fluctuations of the local density of states probe localized surface plasmons on disordered metal films

    Full text link
    We measure the statistical distribution of the local density of optical states (LDOS) on disordered semi-continuous metal films. We show that LDOS fluctuations exhibit a maximum in a regime where fractal clusters dominate the film surface. These large fluctuations are a signature of surface-plasmon localization on the nanometer scale

    Stochastic resonance in periodic potentials: realization in a dissipative optical lattice

    Full text link
    We have observed the phenomenon of stochastic resonance on the Brillouin propagation modes of a dissipative optical lattice. Such a mode has been excited by applying a moving potential modulation with phase velocity equal to the velocity of the mode. Its amplitude has been characterized by the center-of-mass (CM) velocity of the atomic cloud. At Brillouin resonance, we studied the CM-velocity as a function of the optical pumping rate at a given depth of the potential wells. We have observed a resonant dependence of the CM velocity on the optical pumping rate, corresponding to the noise strength. This corresponds to the experimental observation of stochastic resonance in a periodic potential in the low-damping regime
    corecore