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How good is the R.M.S. as a measure of beam size ?
https://cds.cern.ch/record/2048980
CERN. Geneva. Machine Proton Synchotron (MPS) divisionHereward, H GThu, 03 Sep 2015 15:07:15 GMT1969https://cds.cern.ch/record/2048980Higgs boson production in association with top quarks in CMS
https://cds.cern.ch/record/2048908
In this talk searches for Higgs bosons produced in association with top quarks are presented. The searches are performed using the data collected during the first LHC run at a center-of-mass energy of 7 and 8 TeV and results are presented for different Higgs boson decay final states, including bbbar, tautau, WW*/ZZ* and gg, as well as their combination. The talk highlights experimental and theoretical challenges, in particular in view of the upcoming, higher energy LHC run.Caminada, Lea MichaelaThu, 03 Sep 2015 08:36:38 GMT21 Aug 2015CMS-CR-2015-151https://cds.cern.ch/record/2048908Higgs boson properties and tests of the Standard Model at CMS
https://cds.cern.ch/record/2048907
The measurements of the Higgs boson properties, mass, spin/CP, couplings, off-shell cross sections and constraints on invisible width, as well as other Standard model measurements at CMS will be presented. The analysis is based on pp collision data collected at centre-of-mass energies of 7 and 8 TeV by the CMS experiment at the LHC, corresponding to integrated luminosities of 5/fb and 20/fb, respectively.Brandstetter, JohannesThu, 03 Sep 2015 08:36:33 GMT21 Aug 2015CMS-CR-2015-150https://cds.cern.ch/record/2048907Spatial and temporal localization of light in two dimensions
https://cds.cern.ch/record/2048890
Quasi-resonant scattering of light in two dimensions can be described either as a scalar or as a vectorial electromagnetic wave. Performing a scaling analysis we observe in both cases long lived modes, yet only the scalar case exhibits Anderson localized modes together with extremely long mode lifetimes. We show that the localization length of these modes is influenced only by their position, and not their lifetime. Investigating the reasons for the absence of localization, it appears that both the coupling of several polarizations and the presence of near-field terms are able to prevent long lifetimes and Anderson localization.Máximo, Carlos EPiovella, NicolaCourteille, Philippe WKaiser, RobinBachelard, RomainThu, 03 Sep 2015 05:59:50 GMT02 Sep 2015arXiv:1509.00815https://cds.cern.ch/record/2048890Dissipation of Quasiclassical Turbulence in Superfluid $^4$He
https://cds.cern.ch/record/2048889
We compare the decay of turbulence in superfluid $^4$He produced by a moving grid to the decay of turbulence created by either impulsive spin-down to rest or by intense ion injection. In all cases the vortex line density $L$ decays at late time $t$ as $L \propto t^{-3/2}$. At temperatures above 0.8 K, all methods result in the same rate of decay. Below 0.8 K, the spin-down turbulence maintains initial rotation and decays slower than grid turbulence and ion-jet turbulence. This may be due to a decoupling of the large-scale superfluid flow from the normal component at low temperatures, which changes its effective boundary condition from no-slip to slip.Zmeev, D EWalmsley, P MGolov, A IMcClintock, P V EFisher, S NVinen, W FThu, 03 Sep 2015 05:59:50 GMT02 Sep 2015arXiv:1509.00813https://cds.cern.ch/record/2048889Squirming through shear-thinning fluids
https://cds.cern.ch/record/2048888
Many microorganisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in nontrivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problematic.Datt, CharuZhu, LailaiElfring, Gwynn JPak, On ShunThu, 03 Sep 2015 05:59:50 GMT02 Sep 2015arXiv:1509.00810https://cds.cern.ch/record/2048888Chiral plasmon in gapped Dirac systems
https://cds.cern.ch/record/2048887
We study the electromagnetic response and surface electromagnetic modes in a generic gapped Dirac material under pumping with circularly polarized light. The valley imbalance due to pumping leads to a net Berry curvature, giving rise to a finite transverse conductivity. We discuss the appearance of nonreciprocal chiral edge modes, their hybridization and waveguiding in a nanoribbon geometry, and giant polarization rotation in nanoribbon arrays.Kumar, AnshumanNemilentsau, AndreiFung, Kin HungHanson, GeorgeFang, Nicholas XLow, TonyThu, 03 Sep 2015 05:59:49 GMT02 Sep 2015arXiv:1509.00790https://cds.cern.ch/record/2048887Quantifying Gyrotropy in Magnetic Reconnection
https://cds.cern.ch/record/2048886
A new scalar measure of the gyrotropy of a pressure tensor is defined. Previously suggested measures are shown to provide non-physical results in some cases. As examples of its applicability, the new measure is calculated for electron data taken from numerical simulations of magnetic reconnection and shown to sharply outline the separatrices and X-points. Such a diagnostic is potentially useful for spacecraft observations and so a method for calculating it from measurements made in an arbitrary coordinate system is presented.Swisdak, MThu, 03 Sep 2015 05:59:49 GMT02 Sep 2015arXiv:1509.00787https://cds.cern.ch/record/2048886Toroidal membrane vesicles in spherical confinement
https://cds.cern.ch/record/2048885
We investigate the morphology of a toroidal fluid membrane vesicle confined inside a spherical container. The equilibrium shapes are assembled in a geometrical phase diagram as a function of scaled area and reduced volume of the membrane. For small area the vesicle can adopt its free form. When increasing the area, the membrane cannot avoid contact and touches the confining sphere along a circular contact line, which extends to a zone of contact for higher area. The elastic energies of the equilibrium shapes are compared to those of their confined counterparts of spherical topology to predict under which conditions a topology change is favored energetically.Bouzar, LilaMenas, FerhatMüller, Martin MichaelThu, 03 Sep 2015 05:59:48 GMT02 Sep 2015arXiv:1509.00765https://cds.cern.ch/record/2048885Improving absolute gravity estimates by the $L_p$-norm approximation of the ballistic trajectory
https://cds.cern.ch/record/2048884
Iteratively Re-weighted Least Squares (IRLS) were used to simulate the $L_p$-norm approximation of the ballistic trajectory in absolute gravimeters. Two iterations of the IRLS delivered sufficient accuracy of the approximation, with the bias indiscernible in random noise. The simulations were performed for different samplings of the trajectory and different distributions of the data noise. On the platykurtic distributions, the simulations found $L_p$-approximation with $p\approx 3.25$ to yield several times more precise gravity estimates than those obtained with the standard least-squares ($p=2$). The similar improvement at $p\approx 3.5$ was observed on real data measured at the excessive noise conditions.Nagornyi, V DSvitlov, SAraya, AThu, 03 Sep 2015 05:59:48 GMT01 Sep 2015arXiv:1509.00750https://cds.cern.ch/record/2048884Recoil filters for active correlations method: different scenarios
https://cds.cern.ch/record/2048883
New approach to the life time estimation for recoil alpha detected times is presented. Brief description of the Dubna Gas Filled Recoil Separator detection module is presented too. This approach will be used for real time detecting ctive correlationsmethod with nearest future commissioning of new FLNR DC280 extremely high intense heavy ion cyclotron in the year 2017.Tsyganov, Yu SThu, 03 Sep 2015 05:59:48 GMT31 Aug 2015arXiv:1509.00739https://cds.cern.ch/record/2048883Can Bohmian Mechanics Be Made Background Independent?
https://cds.cern.ch/record/2048882
The paper presents an inquiry into the question regarding the compatibility of Bohmian mechanics, intended as a non-local theory of moving point-like particles, with background independence. This issue is worth being investigated because, if the Bohmian framework has to be of some help in developing new physics, it has to be compatible with the most well-established traits of modern physics, background independence being one of such traits. The paper highlights the fact that the notion of background independence in the context of spacetime physics is slippery and interpretation-laden. It is then suggested that the best-matching framework developed by Julian Barbour might provide a robust enough meaning of background independence. The structure of Bohmian dynamics is evaluated against this framework, reaching some intermediate results that speak in favor of the fact that Bohmian mechanics can be made background independent.Vassallo, AntonioThu, 03 Sep 2015 05:59:47 GMT02 Sep 2015arXiv:1509.00734https://cds.cern.ch/record/2048882Time dynamics of photothermal vs optoacoustic response in mid IR nanoscale biospectroscopy
https://cds.cern.ch/record/2048881
Infrared (IR) spectroscopy, a well established tool for chemical analysis of diverse materials, has significant potential in biomedical applications. While the spatial resolution of traditional IR spectroscopy is limited by the wavelength of the IR light to the few micrometres, it has been shown that nanoscale chemical analysis can be obtained by detecting IR induced local heating photothermal response via Scanning Thermal Microscopy (SThM) or local thermomechanical expansion using Atomic Force Microscopy (AFM). This paper explores the potential of a pulsed ps pulse duration high power free electron laser (FEL) light source for AFM-IR and SThM-IR spectroscopy employing standard AFM and SThM probes. The SThM-IR response was found to have a detrimental strong background signal due to the direct heating of the probe, whereas the AFM IR thermomechanical response allowed to eliminate such a problem for both top down and bottom up illuminations with the FEL IR source. The SThM IR characteristic response time was approximately half that of AFM-IR, in line with finite element analysis simulations. Finally, the advantages and drawbacks of AFM-IR wavelength sensitive spectroscopic response using a ps duration FEL vs a high repetition quantum cascade laser IR source in studies of nanoscale dimension amyloid peptide fibres were explored both experimentally and via finite elements analysis.Tovee, Peter DTinker-Mill, ClaireKjoller, KevinAllsop, DavidWeightman, PeterSurman, MarkSiggel-King, Michele R FWolski, AndyKolosov, Oleg VThu, 03 Sep 2015 05:59:47 GMT02 Sep 2015arXiv:1509.00726https://cds.cern.ch/record/2048881Dictionary based Approach to Edge Detection
https://cds.cern.ch/record/2048879
Edge detection is a very essential part of image processing, as quality and accuracy of detection determines the success of further processing. We have developed a new self learning technique for edge detection using dictionary comprised of eigenfilters constructed using features of the input image. The dictionary based method eliminates the need of pre or post processing of the image and accounts for noise, blurriness, class of image and variation of illumination during the detection process itself. Since, this method depends on the characteristics of the image, the new technique can detect edges more accurately and capture greater detail than existing algorithms such as Sobel, Prewitt Laplacian of Gaussian, Canny method etc which use generic filters and operators. We have demonstrated its application on various classes of images such as text, face, barcodes, traffic and cell images. An application of this technique to cell counting in a microscopic image is also presented.Chandra, NitishKhare, KedarThu, 03 Sep 2015 05:59:46 GMT02 Sep 2015arXiv:1509.00714https://cds.cern.ch/record/2048879Stimulated Brillouin scattering revisited: Strong coupling regime and Rabi splitting
https://cds.cern.ch/record/2048878
Stimulated Brillouin scattering in optical waveguides is a fundamental interaction between light and acoustic waves mediated by electrostriction and photoelasticity. In this paper, we revisit the usual theory of this inelastic scattering process to get a joint system in which the acoustic wave is strongly coupled to the interference pattern between the optical waves. We show in particular that, when the optoacoustic coupling rate is comparable to the phonon damping rate, the system enters in the strong coupling regime, giving rise to avoided crossing of the dispersion curve and Rabi-like splitting. We further find that optoacoustic Rabi splitting could in principle be observed using backward stimulated Brillouin scattering in sub-wavelength diameter tapered optical fibers with moderate peak pump power.Huy, Kien PhanBeugnot, Jean-CharlesTchahame, Joel CabrelSylvestre, ThibautThu, 03 Sep 2015 05:59:46 GMT02 Sep 2015arXiv:1509.00709https://cds.cern.ch/record/2048878Present status of source development station at UVSOR-III
https://cds.cern.ch/record/2048877
Construction and development of a source development station are in progress at UVSOR-III, a 750 MeV electron storage ring. It is equipped with an optical klystron type undulator system, a mode lock Ti:Sa Laser system, a dedicated beam-line for visible-VUV radiation and a parasitic beam-line for THz radiation. New light port to extract edge radiation was constructed recently. An optical cavity for a resonator free electron laser is currently being reconstructed. Some experiments such as coherent THz radiation, coherent harmonic radiation, laser Compton Scattering gamma-rays and optical vortices are in progress.Mirian, Najmeh SadatYamazaki, Jun-ichiroHayashi, KenjiKatoh, MasahiroHosaka, MasahitoTakashima, YoshifumiYamamoto, NaotoKonomi, TaroZen, HeishunThu, 03 Sep 2015 05:59:45 GMT02 Sep 2015arXiv:1509.00700https://cds.cern.ch/record/2048877Membrane Mechanics of Endocytosis in Cells with Turgor
https://cds.cern.ch/record/2048876
Endocytosis is an essential process by which cells internalize a piece of plasma membrane and material from the outside. In cells with turgor, pressure opposes membrane defor- mations, and increases the amount of force that has to be generated by the endocytic machinery. To determine this force, and calculate the shape of the membrane, we used physical theory to model an elastic surface under pressure. Accurate fits of experimental profiles are obtained assuming that the coated membrane is highly rigid and preferentially curved at the endocytic site. The forces required from the actin machinery peaks at the onset of deformation, indicating that once invagination has been initiated, endocytosis is unlikely to stall before completion. Coat proteins do not lower the initiation force but may affect the process by the curvature they induce. In the presence of isotropic curvature inducers, pulling the tip of the invagination can trigger the formation of a neck at the base of the invagination. Hence direct neck constriction by actin may not be required, while its pulling role is essential. Finally, the theory shows that anisotropic curvature effectors stabilize membrane invaginations, and the loss of crescent-shaped BAR domain proteins such as Rvs167 could therefore trigger membrane scission.Dmitrieff, SergeNédélec, FrançoisThu, 03 Sep 2015 05:59:45 GMT02 Sep 2015arXiv:1509.00698https://cds.cern.ch/record/2048876Revealing spatially heterogeneous relaxation in a model nanocomposite
https://cds.cern.ch/record/2048875
The detailed nature of spatially heterogeneous dynamics of glycerol-silica nanocomposites is unraveled by combining dielectric spectroscopy with atomistic simulation and statistical mechanical theory. Analysis of the spatial mobility gradient shows no 'glassy' layer, but the alpha relaxation time near the nanoparticle grows with cooling faster than the alpha relaxation time in the bulk, and is ~ 20 times longer at low temperatures. The interfacial layer thickness increases from ~ 1.8 nm at higher temperatures to ~ 3.5 nm upon cooling to near Tg. A real space microscopic description of the mobility gradient is constructed by synergistically combining high temperature atomistic simulation with theory. Our analysis suggests that the interfacial slowing down arises mainly due to an increase of the local cage scale barrier for activated hopping induced by enhanced packing and densification near the nanoparticle surface. The theory is employed to predict how local surface densification can be manipulated to control layer dynamics and shear rigidity over a wide temperature range.Cheng, ShiwangMirigian, StephenCarrillo, Jan-Michael YBocharova, VeraSumpter, Bobby GSchweizer, Kenneth SSokolov, Alexei PThu, 03 Sep 2015 05:59:44 GMT02 Sep 2015arXiv:1509.00688https://cds.cern.ch/record/2048875A generalized Poisson and Poisson-Boltzmann solver for electrostatic environments
https://cds.cern.ch/record/2048874
The computational study of chemical reactions in complex, wet environments is critical for applications in many fields. It is often essential to study chemical reactions in the presence of applied electrochemical potentials, taking into account the non-trivial electrostatic screening coming from the solvent and the electrolytes. As a consequence the electrostatic potential has to be found by solving the generalized Poisson and the Poisson-Boltzmann equation for neutral and ionic solutions, respectively. In the present work solvers for both problems have been developed. A preconditioned conjugate gradient method has been implemented to the generalized Poisson equation and the linear regime of the Poisson-Boltzmann, allowing to solve iteratively the minimization problem with some ten iterations of a ordinary Poisson equation solver. In addition, a self-consistent procedure enables us to solve the non-linear Poisson-Boltzmann problem. Both solvers exhibit very high accuracy and parallel efficiency, and allow for the treatment of different boundary conditions, as for example surface systems. The solver has been integrated into the BigDFT and Quantum-ESPRESSO electronic-structure packages and will be released as an independent program, suitable for integration in other codes.Fisicaro, GGenovese, LAndreussi, OMarzari, NGoedecker, SThu, 03 Sep 2015 05:59:44 GMT02 Sep 2015arXiv:1509.00680https://cds.cern.ch/record/2048874Hierarchical Bayes Ensemble Kalman Filtering
https://cds.cern.ch/record/2048873
Ensemble Kalman filtering (EnKF), when applied to high-dimensional systems, suffers from an inevitably small affordable ensemble size, which results in poor estimates of the background error covariance matrix ${\bf B}$. The common remedy is a kind of regularization, usually an ad-hoc spatial covariance localization (tapering) combined with artificial covariance inflation. Instead of using an ad-hoc regularization, we adopt the idea by Myrseth and Omre (2010) and explicitly admit that the ${\bf B}$ matrix is unknown and random and estimate it along with the state (${\bf x}$) in an optimal hierarchical Bayes analysis scheme. We separate forecast errors into predictability errors (i.e. forecast errors due to uncertainties in the initial data) and model errors (forecast errors due to imperfections in the forecast model) and include the two respective components ${\bf P}$ and ${\bf Q}$ of the ${\bf B}$ matrix into the extended control vector $({\bf x},{\bf P},{\bf Q})$. Similarly, we break the traditional background ensemble into the predictability-error related ensemble and model-error related ensemble. At the observation update (analysis) step, we specify Inverse Wishart based priors for the random matrices ${\bf P}$ and ${\bf Q}$, and conditionally Gaussian prior for the state ${\bf x}$. Then, we update the prior distribution of $({\bf x},{\bf P},{\bf Q})$ using both observation and ensemble data, so that ensemble members are used as generalized observations and ordinary observations are allowed to influence the covariances. An approximation that leads to a practicable analysis algorithm is proposed. Performance of the new filter is studied in numerical experiments with a one-dimensional model of "truth" and "synthetic" observations. The experiments show that the new filter significantly outperforms EnKF in a wide range of filtering regimes.Tsyrulnikov, MichaelRakitko, AlexanderThu, 03 Sep 2015 05:59:43 GMT02 Sep 2015arXiv:1509.00652https://cds.cern.ch/record/2048873Localization without recurrence and pseudo-Bloch oscillations in optics
https://cds.cern.ch/record/2048872
Dynamical localization, i.e. the absence of secular spreading of a quantum or classical wave packet, is usually associated to Hamiltonians with purely point spectrum, i.e. with a normalizable and complete set of eigenstates, which show quasi-periodic dynamics (recurrence). Here we show rather counter-intuitively that dynamical localization can be observed in Hamiltonians with absolutely continuous spectrum, where recurrence effects are forbidden. An optical realization of such an Hamiltonian is proposed based on beam propagation in a self-imaging optical resonator with a phase grating. Localization without recurrence in this system is explained in terms of pseudo-Bloch optical oscillations.Longhi, StefanoThu, 03 Sep 2015 05:59:43 GMT02 Sep 2015arXiv:1509.00648https://cds.cern.ch/record/2048872Dynamic power balance for nonlinear waves in unbalanced gain and loss landscapes
https://cds.cern.ch/record/2048870
The presence of losses in nonlinear photonic structures is a crucial issue for modern applications. Active parts are introduced for wave power compensation resulting in unbalanced gain and loss landscapes where localized beam propagation is, in general, dynamically unstable. Here we provide generic sufficient conditions for the relation between the gain-loss and the refractive index profiles in order to ensure efficient wave trapping and stable propagation for a wide range of beam launching conditions such as initial power, angle of incidence and position. The stability is a consequence of an underlying dynamic power balance mechanism related to a conserved quantity of wave dynamics.Kominis, YannisThu, 03 Sep 2015 05:59:43 GMT02 Sep 2015arXiv:1509.00628https://cds.cern.ch/record/2048870Controllable long-range interactions between dark solitons in dipolar condensates
https://cds.cern.ch/record/2048868
We study the family of static and moving dark solitons in quasi-one-dimensional dipolar Bose-Einstein condensates, exploring their modified form and interactions. The density dip of the soliton acts as a giant anti-dipole which adds a long-range contribution to the conventional short-range soliton-soliton interaction. We map out the stability diagram as a function of the strength and polarization direction of the atomic dipoles, identifying both roton and phonon instabilities. Away from these instabilities, the solitons collide elastically. Varying the polarization direction relative to the condensate axis enables tuning of this non-local interaction between repulsive and attractive; the latter case supports unusual dark soliton bound states.Bland, TEdmonds, M JProukakis, N PMartin, A MO'Dell, D H JParker, N GThu, 03 Sep 2015 05:59:42 GMT02 Sep 2015arXiv:1509.00615https://cds.cern.ch/record/2048868Nonlinear analysis on purely mechanical stabilization of a wheeled inverted pendulum on a slope
https://cds.cern.ch/record/2048867
This paper investigates the potential for stabilizing an inverted pendulum without electric devices, using gravitational potential energy. We propose a wheeled mechanism on a slope, specifically, a wheeled double pendulum, whose second pendulum transforms gravity force into braking force that acts on the wheel. In this paper, we derive steady-state equations of this system and conduct nonlinear analysis to obtain parameter conditions under which the standing position of the first pendulum becomes asymptotically stable. In this asymptotically stable condition, the proposed mechanism descends the slope in a stable standing position, while dissipating gravitational potential energy via the brake mechanism. By numerically continuing the stability limits in the parameter space, we find that the stable parameter region is simply connected. This implies that the proposed mechanism can be robust against errors in parameter setting.Yoshida, KatsutoshiSekikawa, MunehisaHosomi, KentaThu, 03 Sep 2015 05:59:42 GMT02 Sep 2015arXiv:1509.00605https://cds.cern.ch/record/2048867Axial Creeping Flow in the Gap between a Rigid Cylinder and a Concentric Elastic Tube
https://cds.cern.ch/record/2048866
We examine transient axial creeping flow in the annular gap between a rigid cylinder and a concentric elastic tube. The gap is initially filled with a thin fluid layer. The study focuses on viscous-elastic time-scales for which the rate of solid deformation is of the same order-of-magnitude as the velocity of the fluid. We employ an elastic shell model and the lubrication approximation to obtain a forced nonlinear diffusion equation governing the viscous-elastic interaction. In the case of an advancing liquid front into a configuration with a negligible film layer (compared with the radial deformation of the elastic tube), the governing equation degenerates into a forced porous medium equation, for which several closed-form solutions are presented. In the case where the initial film layer is non-negligible, self-similarity is used to devise propagation laws for a pressure driven liquid front. When advancing external forces are applied on the tube, the formation of dipole structures is shown to dominate the initial stages of the induced flow and deformation regimes. These are variants of the dipole solution of the porous medium equation. Finally, since the rate of pressure propagation decreases with the height of the liquid film, we show that isolated moving deformation patterns can be created and superimposed to generate a moving wave-like deformation field. The presented interaction between viscosity and elasticity may be applied to fields such as soft-robotics and micro-scale or larger swimmers by allowing for the time-dependent control of an axisymmetric compliant boundary.Elbaz, Shai BGat, Amir DThu, 03 Sep 2015 05:59:42 GMT02 Sep 2015arXiv:1509.00604https://cds.cern.ch/record/2048866