431 research outputs found

    NRQCD Results on Form Factors

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    We report results on fBf_B and semi-leptonic BB decay form factors using NRQCD. We investigate 1/M1/M scaling behavior of decay amplitudes. For fBf_B Effect of higher order relativistic correction terms are also studied.Comment: 9 pgs. 10 figures. Latex2e. espcrc2.sty included. Talk presented at the Internatioal Workshop "LATTICE QCD ON PARALLEL COMPUTERS", March 1997, Tsukub

    Heavy quark mass dependence of semileptonic form factors for B decays

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    We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass MPSM_{PS}. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the O(a)O(a)-improved clover action at β=5.9\beta=5.9 on a 163×4016^3\times 40 and 243×6424^3\times 64 lattice. We find that a weak dependence of form factors on MPSM_{PS} observed in previous studies in the region of charm quark persists up to the region ofbb quark. The soft pion relation f0(qmax2)=fB/fπf^0(q^2_{max})=f_B/f_\pi is examined and found to be largely violated.Comment: 3 pages, latex source-file, 4 figures as epsf-file, uses espcrc2.sty. Talk presented by S. Tominaga at Lattice 97, Edinburgh, Scotland, 22-26 Jul 199

    Gauge Theories on a 2+2 Anisotropic Lattice

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    The implementation of gauge theories on a four-dimensional anisotropic lattice with two distinct lattice spacings is discussed, with special attention to the case where two axes are finely and two axes are coarsely discretized. Feynman rules for the Wilson gauge action are derived and the renormalizability of the theory and the recovery of the continuum limit are analyzed. The calculation of the gluon propagator and the restoration of Lorentz invariance in on-shell states is presented to one-loop order in lattice perturbation theory for SU(Nc)SU(N_c) on both 2+2 and 3+1 lattices.Comment: 27 pages, uses feynmf. Font compatibility adjuste

    Victim-offender mediation and social work: focus groups with mediators in Flanders

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    The role of social work in the restorative justice field remains largely unexplored. This article reports on the findings of focus groups conducted with mediators of juvenile and adult mediation practices in Flanders (Belgium) to gain more insight into how mediators perceive their professional role and to what extent they refer to individual and structural dimensions of social work practice. Implications for future social work involvement and research are made

    Potential Models for Radiative Rare B Decays

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    We compute the branching ratios for the radiative rare decays of B into K-Meson states and compare them to the experimentally determined branching ratio for inclusive decay b -> s gamma using non relativistic quark model, and form factor definitions consistent with HQET covariant trace formalism. Such calculations necessarily involve a potential model. In order to test the sensitivity of calculations to potential models we have used three different potentials, namely linear potential, screening confining potential and heavy quark potential as it stands in QCD.We find the branching ratios relative to the inclusive b ->s gamma decay to be (16.07\pm 5.2)% for B -> K^* (892)gamma and (7.25\pm 3.2)% for B -> K_2^* (1430)gamma for linear potential. In the case of the screening confining potential these values are (19.75\pm 5.3)% and (4.74\pm 1.2)% while those for the heavy quark potential are (11.18\pm 4.6)% and (5.09\pm 2.7)% respectively. All these values are consistent with the corresponding present CLEO experimental values: (16.25\pm 1.21)% and (5.93\pm 0.46)%.Comment: RevTeX, 6 pages, 1 eps figur

    QCD Sum Rule Analysis of the Decays B→Kℓ+ℓ−B \to K \ell^+ \ell^- and B→K∗ℓ+ℓ−B \to K^* \ell^+ \ell^-

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    We use QCD sum rules to calculate the hadronic matrix elements governing the rare decays B→Kℓ+ℓ−B \to K \ell^+ \ell^- and B→K∗ℓ+ℓ−B \to K^* \ell^+ \ell^- induced by the flavour changing neutral current b→sb \to s transition. We also study relations among semileptonic and rare B→K(∗)B \to K^{(*)} decay form factors. The analysis of the invariant mass distribution of the lepton pair in B→K(∗)ℓ+ℓ−B \to K^{(*)} \ell^+ \ell^- and of the angular asymmetry in B→K∗ℓ+ℓ−B \to K^* \ell^+ \ell^- provides us with interesting tests of the Standard Model and its extensions.Comment: 26 pages REVTEX + 7 figures. Some typos corrected, figure 5 and 7 modified. This version will appear on Physical Review

    The transition form factors for semi-leptonic weak decays of J/ψJ/\psi in QCD sum rules

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    Within the Standard Model, we investigate the semi-leptonic weak decays of J/ψJ/\psi. The various form factors of J/ψJ/\psi transiting to a single charmed meson (D(d,s)(∗)D^{(*)}_{(d,s)}) are studied in the framework of the QCD sum rules. These form factors fully determine the rates of the weak semi-leptonic decays of J/ψJ/\psi and provide valuable information about the non-perturbative QCD effects. Our results indicate that the decay rate of the semi-leptonic weak decay mode J/ψ→Ds(∗)−+e++νeJ/\psi \to D^{(*)-}_{s}+e^{+}+\nu_{e} is at order of 10−1010^{-10}.Comment: 28 pages, 6 figures, revised version to be published in Eur.Phys.J.

    Passerine Birds Breeding under Chronic Noise Experience Reduced Fitness

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    Background Fitness in birds has been shown to be negatively associated with anthropogenic noise, but the underlying mechanisms remain obscure. It is however crucial to understand the mechanisms of how urban noise impinges on fitness to obtain a better understanding of the role of chronic noise in urban ecology. Here, we examine three hypotheses on how noise might reduce reproductive output in passerine birds: (H1) by impairing mate choice, (H2) by reducing territory quality and (H3) by impeding chick development. Methodology/Principal Findings We used long-term data from an island population of house sparrows, Passer domesticus, in which we can precisely estimate fitness. We found that nests in an area affected by the noise from large generators produced fewer young, of lower body mass, and fewer recruits, even when we corrected statistically for parental genetic quality using a cross-fostering set-up, supporting H3. Also, individual females provided their young with food less often when they bred in the noisy area compared to breeding attempts by the same females elsewhere. Furthermore, we show that females reacted flexibly to increased noise levels by adjusting their provisioning rate in the short term, which suggests that noise may be a causal factor that reduces reproductive output. We rejected H1 and H2 because nestbox occupancy, parental body mass, age and reproductive investment did not differ significantly between noisy and quiet areas. Conclusions/Significance Our results suggest a previously undescribed mechanism to explain how environmental noise can reduce fitness in passerine birds: by acoustically masking parent–offspring communication. More importantly, using a cross-fostering set-up, our results demonstrate that birds breeding in a noisy environment experience significant fitness costs. Chronic noise is omnipresent around human habitation and may produces similar fitness consequences in a wide range of urban bird species

    Demystifying image-based machine learning: a practical guide to automated analysis of field imagery using modern machine learning tools

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    Image-based machine learning methods are becoming among the most widely-used forms of data analysis across science, technology, engineering, and industry. These methods are powerful because they can rapidly and automatically extract rich contextual and spatial information from images, a process that has historically required a large amount of human labor. A wide range of recent scientific applications have demonstrated the potential of these methods to change how researchers study the ocean. However, despite their promise, machine learning tools are still under-exploited in many domains including species and environmental monitoring, biodiversity surveys, fisheries abundance and size estimation, rare event and species detection, the study of animal behavior, and citizen science. Our objective in this article is to provide an approachable, end-to-end guide to help researchers apply image-based machine learning methods effectively to their own research problems. Using a case study, we describe how to prepare data, train and deploy models, and overcome common issues that can cause models to underperform. Importantly, we discuss how to diagnose problems that can cause poor model performance on new imagery to build robust tools that can vastly accelerate data acquisition in the marine realm. Code to perform analyses is provided at https://github.com/heinsense2/AIO_CaseStudy
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