Results 1 - 10 of 5012
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[en] The preliminary results of measurement of the e+ e− → π+π−π0 cross section in the 1.05–2 GeV center-of-mass energy range with 30 pb–1 of experimental data collected using the CMD-3 detector are presented. The parameters of resonant states ω(1420) and ω(1650) are obtained.
[en] The center of buoyancy of an arbitrary shaped body is defined in analogy to the center of gravity. The definitions of the buoyant force and center of buoyancy in terms of integrals over the area of the body are converted to volume integrals and shown to have simple intuitive interpretations
[en] Novel and supersymmetric extensions of the Calogero-Sutherland hyperbolic systems are obtained by gauging the isometry of matrix superfield models. The bosonic core of the models is the standard Calogero-Sutherland hyperbolic system, whereas the model contains additional semi-dynamical spin variables and is an extension of the U(2) spin Calogero-Sutherland hyperbolic system. We construct two different versions of the model, with and without the interacting center-of-mass coordinate in the bosonic sector.
[en] The dynamics of a cylinder rolling on a horizontal plane acted on by an external force applied at an arbitrary angle is studied with emphasis on the directions of the acceleration of the centre-of-mass and the angular acceleration of the body. If rolling occurs without slipping, there is a relationship between the directions of these accelerations. If the linear acceleration points to the right, then the angular acceleration is clockwise. On the other hand, if it points to the left, then the angular acceleration is counterclockwise. In contrast, if rolling and slipping occurs, the direction of the linear acceleration does not determine the direction of the angular acceleration. For example, the linear acceleration may point to the right and the angular acceleration clockwise or counterclockwise depending on the external force orientation and point of application.
[en] We consider the simple and classical theorem of the motion of the centre of mass, pointing out that many textbooks append a wrong corollary to it: that the motion of the centre of mass is always independent from the internal forces. We give an explicit example showing that this corollary is wrong. We discuss using a historical approach the genesis of such a misunderstanding. The contents of the paper may be used at different levels of complexity. The explicit example may be used to discuss the theorem at an undergraduate level in a clearer way than usual, but the paper also contains much for an advanced course on classical mechanics. Moreover, the historical approach may also be of interest in the study of the philosophy and sociology of science.
[en] We propose a kinematical enhancement of the tt¯ charge asymmetry at the LHC by selecting events with the tt¯ centre of mass frame highly boosted along the beam axis. This kinematical selection increases the asymmetries and their significance up to a factor of two in a rather model-independent fashion. Hence, it can be a perfect complement to enhance model discrimination at the LHC.
[en] For the upgrade of the DAQ of the CMS experiment in 2013/2014 an interface between the custom detector Front End Drivers (FEDs) and the new DAQ eventbuilder network has to be designed. For a loss-less data collection from more then 600 FEDs a new FPGA based card implementing the TCP/IP protocol suite over 10Gbps Ethernet has been developed. We present the hardware challenges and protocol modifications made to TCP in order to simplify its FPGA implementation together with a set of performance measurements which were carried out with the current prototype
[en] We evaluate numerically the probability of linking, i.e. the probability of a given pair of self-avoiding polygons (SAPs) being entangled and forming a nontrivial link type L. In the simulation we generate pairs of SAPs of N spherical segments of radius rd such that they have no overlaps among the segments and each of the SAPs has the trivial knot type. We evaluate the probability of a self-avoiding pair of SAPs forming a given link type L for various link types with fixed distance R between the centers of mass of the two SAPs. We define normalized distance r by r=R/Rg,01 where Rg,01 denotes the square root of the mean square radius of gyration of SAP of the trivial knot 01. We introduce formulae expressing the linking probability as a function of normalized distance r, which gives good fitting curves with respect to χ2 values. We also investigate the dependence of linking probabilities on the excluded-volume parameter rd and the number of segments, N. Quite interestingly, the graph of linking probability versus normalized distance r shows no N-dependence at a particular value of the excluded volume parameter, rd = 0.2
[en] Quantum communication over long distances relies on the ability to create entanglement between two remote quantum nodes. Recent proposals aiming at experimental realization propose a hybrid quantum repeater setup where two distant material qubits are entangled by light–matter interaction. Motivated by these developments, we investigate possible decoherence effects originating from the centre-of-mass motion of the spatially well-separated trapped qubits. Within the Lamb–Dicke regime we use photon exchange involving coherent states of the radiation field to entangle the two material qubits. Optimal generalized photonic field measurements are used to achieve entangled qubit pairs with high fidelities and high success probabilities. We demonstrate that the quality of the achievable two-qubit entanglement crucially depends on the trap frequencies involved. Furthermore, dynamical decoupling schemes are proposed which are capable of suppressing centre-of-mass motion-induced decoherence effects significantly and which involve only local operations acting on the spatially well-separated material qubits. (paper)