127 research outputs found

    Experiments of closely coupled monopoles with load matching in a random field

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    Recent theoretical and simulation studies reveal that closely coupled antennas with appropriately chosen impedance matching loads can yield desired characteristics of small antenna correlation coefficients and/or high received power levels. However, no experiment has been performed to verify these claims. Here, we describe an experimental setup used to investigate the correlation and received power of closely coupled antennas with impedance matching. Specifically, a two-monopole array with a small antenna spacing 0.05 wavelength and five different matching networks are constructed and measured. Whereas our experimental results largely confirm theoretical predictions, some discrepancies due to simplifications made in the theoretical models are observed

    The Longitudinal Polarimeter at HERA

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    The design, construction and operation of a Compton back-scattering laser polarimeter at the HERA storage ring at DESY are described. The device measures the longitudinal polarization of the electron beam between the spin rotators at the HERMES experiment with a fractional systematic uncertainty of 1.6%. A measurement of the beam polarization to an absolute statistical precision of 0.01 requires typically one minute when the device is operated in the multi-photon mode. The polarimeter also measures the polarization of each individual electron bunch to an absolute statistical precision of 0.06 in approximately five minutes. It was found that colliding and non-colliding bunches can have substantially different polarizations. This information is important to the collider experiments H1 and ZEUS for their future longitudinally polarized electron program because those experiments use the colliding bunches only.Comment: 21 pages (Latex), 14 figures (EPS

    Benchmark problem definition and cross-validation for characteristic mode solvers

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    In October 2016, the Special Interest Group on Theory of Characteristic Modes (TCM) initiated a coordinated effort to perform benchmarking work for characteristic mode (CM) analysis. The primary purpose is to help improve the reliability and capability of existing CM solvers and to provide the means for validating future tools. Significant progress has already been made in this joint activity. In particular, this paper describes several benchmark problems that were defined and analyzes some results from the cross-validations of different CM solvers using these problems. The results show that despite differences in the implementation details, good agreement is observed in the calculated eigenvalues and eigencurrents across the solvers. Finally, it is concluded that future work should focus on understanding the impact of common parameters and output settings to further reduce variability in the results

    Strong Decays of Strange Quarkonia

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    In this paper we evaluate strong decay amplitudes and partial widths of strange mesons (strangeonia and kaonia) in the 3P0 decay model. We give numerical results for all energetically allowed open-flavor two-body decay modes of all nsbar and ssbar strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and 1F multiplets, comprising strong decays of a total of 43 resonances into 525 two-body modes, with 891 numerically evaluated amplitudes. This set of resonances includes all strange qqbar states with allowed strong decays expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic quark model SHO wavefunctions to evaluate these amplitudes, and quote numerical results for all amplitudes present in each decay mode. We also discuss the status of the associated experimental candidates, and note which states and decay modes would be especially interesting for future experimental study at hadronic, e+e- and photoproduction facilities. These results should also be useful in distinguishing conventional quark model mesons from exotica such as glueballs and hybrids through their strong decays.Comment: 69 pages, 5 figures, 39 table

    Probing the strength of infants' preference for helpers over hinderers: two replication attempts of Hamlin and Wynn (2011)

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    Several studies indicate that infants prefer individuals who act prosocially over those who act antisocially toward unrelated third parties. In the present study, we focused on a paradigm published by Kiley Hamlin and Karen Wynn in 2011. In this study, infants were habituated to a live puppet show in which a protagonist tried to open a box to retrieve a toy placed inside. The protagonist was either helped by a second puppet (the “Helper”), or hindered by a third puppet (the “Hinderer”). At test, infants were presented with the Helper and the Hinderer, and encouraged to reach for one of them. In the original study, 75% of 9-month-olds selected the Helper, arguably demonstrating a preference for prosocial over antisocial individuals. We conducted two studies with the aim of replicating this result. Each attempt was performed by a different group of experimenters. Study 1 followed the methods of the published study as faithfully as possible. Study 2 introduced slight modifications to the stimuli and the procedure following the guidelines generously provided by Kiley Hamlin and her collaborators. Yet, in our replication attempts, 9-month-olds’ preference for helpers over hinderers did not differ significantly from chance (62.5% and 50%, respectively, in Studies 1 and 2). Two types of factors could explain why our results differed from those of Hamlin and Wynn: minor methodological dissimilarities (in procedure, materials, or the population tested), or the effect size being smaller than originally assumed. We conclude that fine methodological details that are crucial to infants’ success in this task need to be identified to ensure the replicability of the original result

    Observation of a 1750 MeV/c^2 Enhancement in the Diffractive Photoproduction of K^+K^-

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    Using the FOCUS spectrometer with photon beam energies between 20 and 160 \gev, we confirm the existence of a diffractively photoproduced enhancement in K+KK^+K^- at 1750 \mevcc with nearly 100 times the statistics of previous experiments. Assuming this enhancement to be a single resonance with a Breit-Wigner mass shape, we determine its mass to be 1753.5±1.5±2.31753.5\pm 1.5\pm 2.3 \mevcc and its width to be 122.2±6.2±8.0122.2\pm 6.2\pm 8.0 \mevcc. We find no corresponding enhancement at 1750 \mevcc in KKK^*K, and again neglecting any possible interference effects we place limits on the ratio Γ(X(1750)KK)/Γ(X(1750)K+K)\Gamma (X(1750) \to K^*K)/\Gamma (X(1750) \to K^+K^-). Our results are consistent with previous photoproduction experiments, but, because of the much greater statistics, challenge the common interpretation of this enhancement as the ϕ(1680)\phi (1680) seen in e+ee^+e^- annihilation experiments.Comment: 10 pages, 5 figure

    The influence of intention, outcome and question-wording on children's and adults' moral judgments

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    The influence of intention and outcome information on moral judgments was investigated by telling children aged 4-8 years and adults (N=169) stories involving accidental harms (positive intention, negative outcome) or attempted harms (negative intention, positive outcome) from two studies (Helwig, Zelazo, & Wilson, 2001; Zelazo, Helwig, & Lau, 1996). When the original acceptability (wrongness) question was asked, the original findings were closely replicated: children’s and adults’ acceptability judgments, and children’s punishment judgments, were primarily outcome-based. However, when this question was rephrased, 4-5-year-olds’ judgments were approximately equally influenced by intention and outcome, and from 5-6 years they were primarily intention-based. These findings indicate that, for methodological reasons, children’s (and adults’) ability to make intention-based judgment has often been substantially underestimated

    Results of final focus test beam

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    International audienceThe beam experiments of Final Focus Test Beam (FFTB) started in September 1993 at SLAC, and have produced a 1.7 μm×75 nm spot of 46 GeV electron beam. A number of new techniques involving two nanometer spot-size monitors have been developed. Several beam diagnostic/tuning schemes are applied to achieve and maintain the small spot. This experiment opens the way toward the nanometer world for future linear collider
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