25,133 research outputs found

    Ξ›bβ†’Ξ›cτνˉτ\Lambda_b\to\Lambda_c\tau\bar\nu_\tau decay in scalar and vector leptoquark scenarios

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    It has been shown that the anomalies observed in BΛ‰β†’D(βˆ—)τνˉτ\bar B\to D^{(\ast)}\tau\bar\nu_\tau and BΛ‰β†’KΛ‰β„“+β„“βˆ’\bar B\to \bar K\ell^+\ell^- decays can be resolved by adding a single scalar or vector leptoquark to the Standard Model, while constraints from other precision measurements in the flavour sector can be satisfied without fine-tuning. To further explore these two interesting scenarios, in this paper, we study their effects in the semi-leptonic Ξ›bβ†’Ξ›cτνˉτ\Lambda_b\to\Lambda_c\tau\bar\nu_\tau decay. Using the best-fit solutions for the operator coefficients allowed by the current data of mesonic decays, we find that (i) the two scenarios give similar amounts of enhancements to the branching fraction B(Ξ›bβ†’Ξ›cτνˉτ)\mathcal B(\Lambda_b\to\Lambda_c\tau\bar\nu_\tau) and the ratio RΞ›c=B(Ξ›bβ†’Ξ›cτνˉτ)/B(Ξ›bβ†’Ξ›cβ„“Ξ½Λ‰β„“)R_{\Lambda_c}=\mathcal B(\Lambda_b\to\Lambda_c \tau\bar\nu_\tau)/\mathcal B(\Lambda_b\to\Lambda_c\ell\bar\nu_\ell), (ii) the two best-fit solutions in each of these two scenarios are also indistinguishable from each other, (iii) both scenarios give nearly the same predictions as those of the Standard Model for the longitudinal polarizations of Ξ›c\Lambda_c and Ο„\tau as well as the lepton-side forward-backward asymmetry. With future measurements of these observables in Ξ›bβ†’Ξ›cτνˉτ\Lambda_b\to\Lambda_c\tau\bar\nu_\tau decay at the LHCb, the two leptoquark scenarios could be further tested, and even differentiated from the other NP explanations for the RD(βˆ—)R_{D^{(\ast)}} anomalies. We also discuss the feasibility for the measurements of these observables at the LHC and the future e+eβˆ’e^+e^- colliders.Comment: 29 pages, 4 tables and 2 figures; More references and the feasibility for the measurements of the observables in these decays at the LHC and the future e+eβˆ’e^+e^- colliders added, final version published in the journa

    Cross-Domain Image Retrieval with Attention Modeling

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    With the proliferation of e-commerce websites and the ubiquitousness of smart phones, cross-domain image retrieval using images taken by smart phones as queries to search products on e-commerce websites is emerging as a popular application. One challenge of this task is to locate the attention of both the query and database images. In particular, database images, e.g. of fashion products, on e-commerce websites are typically displayed with other accessories, and the images taken by users contain noisy background and large variations in orientation and lighting. Consequently, their attention is difficult to locate. In this paper, we exploit the rich tag information available on the e-commerce websites to locate the attention of database images. For query images, we use each candidate image in the database as the context to locate the query attention. Novel deep convolutional neural network architectures, namely TagYNet and CtxYNet, are proposed to learn the attention weights and then extract effective representations of the images. Experimental results on public datasets confirm that our approaches have significant improvement over the existing methods in terms of the retrieval accuracy and efficiency.Comment: 8 pages with an extra reference pag
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