Micromagnetic Simulation of Nanoscale Films with Perpendicular Anisotropy

A model is studied for the theoretical description of nanoscale magnetic films with high perpendicular anisotropy. In the model the magnetic film is described in terms of single domain magnetic grains with Ising-like behavior, interacting via exchange as well as via dipolar forces. Additionally, the model contains an energy barrier and a coupling to an external magnetic field. Disorder is taken into account in order to describe realistic domain and domain wall structures. The influence of a finite temperature as well as the dynamics can be modeled by a Monte Carlo simulation. Many of the experimental findings can be investigated and at least partly understood by the model introduced above. For thin films the magnetisation reversal is driven by domain wall motion. The results for the field and temperature dependence of the domain wall velocity suggest that for thin films hysteresis can be described as a depinning transition of the domain walls rounded by thermal activation for finite temperatures.Comment: Revtex, Postscript Figures, to be published in J. Appl.Phy

Study of Scalar Top Quarks in the Neutralino and Chargino Decay Channel

The scalar top discovery potential has been studied with a full-statistics background simulation at sqrt(s)=500 GeV and L = 500 fb-1 for the TESLA project. The beam polarization is very important to measure the scalar top mixing angle and to determine its mass. The latest estimation of the beam polarization parameters is applied. This study includes e+ polarization, which improves the sensitivity. For a 180 GeV scalar top at minimum production cross section, we obtain delta(m) = 0.8 GeV and delta(cosT) = 0.008 in the neutralino decay channel, and delta(m) = 0.5 GeV and delta(cosT) = 0.004 in the chargino decay channel.Comment: 4 pages, 6 figures, Proc. LCWS Chicago, November 200

A Highly Selective First-Level Muon Trigger With MDT Chamber Data for ATLAS at HL-LHC

Highly selective triggers are essential for the physics programme of the ATLAS experiment at HL-LHC where the instantaneous luminosity will be about an order of magnitude larger than the LHC instantaneous luminosity in Run 1. The first level muon trigger rate is dominated by low momentum muons below the nominal trigger threshold due to the moderate momentum resolution of the Resistive Plate and Thin Gap trigger chambers. The resulting high trigger rates at HL-LHC can be sufficiently reduced by using the data of the precision Muon Drift Tube chambers for the trigger decision. This requires the implementation of a fast MDT read-out chain and of a fast MDT track reconstruction algorithm with a latency of at most 6 microseconds. A hardware demonstrator of the fast read-out chain has been successfully tested at the HL-LHC operating conditions at the CERN Gamma Irradiation Facility. The fast track reconstruction algorithm has been implemented on a fast trigger processor

Executive compensation and the susceptibility of firms to hostile takeovers : An empirical investigation of the U.S. oil industry

We investigate the suggested substitutive relation between executive compensation and the disciplinary threat of takeover imposed by the market for corporate control. We complement other empirical studies on managerial compensation and corporate control mechanisms in three distinct ways. First, we concentrate on firms in the oil industry for which agency problems were especially severe in the 1980s. Due to the extensive generation of excess cash flow, product and factor market discipline was ineffective. Second, we obtain a unique data set drawn directly from proxy statements which accounts not only for salary and bonus but for the value of all stock-market based compensation held in the portfolio of a CEO. Our data set consists of 51 firms in the U.S. oil industry from 1977 to 1994. Third, we employ ex ante measures of the threat of takeover at the individual firm level which are superior to ex post measures like actual takeover occurrence or past incidence of takeovers in an industry. Results show that annual compensation and, to a much higher degree, stock-based managerial compensation increase after a firm becomes protected from a hostile takeover. However, clear-cut evidence that CEOs of protected firms receive higher compensation than those of firms considered susceptible to a takeover cannot be found

Radiative return method as a tool in hadronic physics

A short review of both theoretical and experimental aspects of the radiative return method is presented. It is emphasised that the method gives not only possibility of the independent from the scan method measurement of the hadronic cross section, but also can provide information concerning details of the hadronic interactions. New developments in the PHOKHARA event generator are also reviewed. The 3 pion and kaon pair production is implemented within the version 5.0 of the program, together with contributions of the radiative phi decays to the 2 pion final states. Missing NLO radiative corrections to the e+e- -> mu+ mu- gamma process will be implemented in the forthcoming version of the generator

Evolutionary Markovian Strategies in 2 x 2 Spatial Games

Evolutionary spatial 2 x 2 games between heterogeneous agents are analyzed using different variants of cellular automata (CA). Agents play repeatedly against their nearest neighbors 2 x 2 games specified by a rescaled payoff matrix with two parameteres. Each agent is governed by a binary Markovian strategy (BMS) specified by 4 conditional probabilities [p_R, p_S, p_T, p_P] that take values 0 or 1. The initial configuration consists in a random assignment of "strategists" among the 2^4= 16 possible BMS. The system then evolves within strategy space according to the simple standard rule: each agent copies the strategy of the neighbor who got the highest payoff. Besides on the payoff matrix, the dominant strategy -and the degree of cooperation- depend on i) the type of the neighborhood (von Neumann or Moore); ii) the way the cooperation state is actualized (deterministically or stochastichally); and iii) the amount of noise measured by a parameter epsilon. However a robust winner strategy is [1,0,1,1].Comment: 18 pages, 8 figures (7 of these figures contain 4 encapsulapted poscript files each

Modeling the X-ray Contribution of X-ray Binary Jets

Astrophysical jets exist in both XRBs and AGN, and seem to share common features, particularly in the radio. While AGN jets are known to emit X-rays, the situation for XRB jets is not so clear. Radio jets have been resolved in several XRBs in the low/hard state, establishing that some form of outflow is routinely present in this state. Interestingly, the flat-to-inverted radio synchrotron emission associated with these outflows strongly correlates with the X-ray emission in several sources, suggesting that the jet plasma plays a role at higher frequencies. In this same state, there is increasing evidence for a turnover in the IR/optical where the flat-to-inverted spectrum seems to connect to an optically thin component extending into the X-rays. We discuss how jet synchrotron emission is likely to contribute to the X-rays, in addition to inverse Compton up-scattering, providing a natural explanation for these correlations and the turnover in the IR/optical band. We present model parameters for fits to several sources, and address some common misconceptions about the jet model.Comment: 4 pages, 1 Table, conference proceedings for "The Physics of Relativistic Jets in the Chandra and XMM Era, Bologna, 2002", Eds. G. Brunetti, D. E. Harris, R. M. Sambruna & G. Sett