3,919 research outputs found

    Status of neutrino oscillations I: the three-neutrino scenario

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    We present a global analysis of neutrino oscillation data within the three-neutrino oscillation scheme, including in our fit all the current solar neutrino data, the reactor neutrino data from KamLAND and CHOOZ, the atmospheric neutrino data from Super-Kamiokande and MACRO, and the first data from the K2K long-baseline accelerator experiment. We determine the current best fit values and allowed ranges for the three-flavor oscillation parameters, discussing the relevance of each individual data set as well as the complementarity of different data sets. Furthermore, we analyze in detail the status of the small parameters theta_13 and Delta_m21^2 / Delta_m31^2, which fix the possible strength of CP violating effects in neutrino oscillations.Comment: 13 pages, LaTeX file using JHEP3, 5 figures included. Talk given at the International Workshop on Astroparticle and High Energy Physics (AHEP-2003), Valencia, Spain, 14-18 October 200

    Bounds on extra quark-lepton generations from precision measurements

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    The existence of extra chiral generations is strongly disfavored by the precision electroweak data if all the extra fermions are heavier than m_Z. However fits as good as the SM can be obtained if one allows the new neutral leptons to have masses close to 50 GeV. In the framework of SUSY models precision measurements cannot exclude one additional generation of heavy fermions if chargino and neutralino have masses around 60 GeV with delta_m around 1 GeV.Comment: 4 pages, LaTeX, 4 figures included. Talk given at PASCOS99 conference, Lake Tahoe, California, December 10-16, 199

    Sterile neutrinos after the first MiniBooNE results

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    In view of the recent results from the MiniBooNE experiment we revisit the global neutrino oscillation fit to short-baseline neutrino data by adding one, two or three sterile neutrinos with eV-scale masses to the three Standard Model neutrinos. We find that four-neutrino oscillations of the (3+1) type, which have been only marginally allowed before the recent MiniBooNE results, become even more disfavored with the new data. In the framework of so-called (3+2) five-neutrino mass schemes the MiniBooNE results can be nicely reconciled with the LSND appearance evidence thanks to the possibility of CP violation available in such oscillation schemes; however, the tension between appearance and disappearance experiments represents a serious problem in (3+2) schemes, so that these models are ultimately not viable. This tension remains also when a third sterile neutrino is added, and we do not find a significant improvement of the global fit in a (3+3) scheme.Comment: 5 pages, LaTeX file using jpconf style, 3 figures included. Proceedings of "The 2007 Europhysics Conference on High Energy Physics", Manchester, England, July 19-25, 2007. Typos correcte

    Sterile neutrino oscillations after first MiniBooNE results

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    In view of the recent results from the MiniBooNE experiment we revisit the global neutrino oscillation fit to short-baseline neutrino data by adding one or two sterile neutrinos with eV-scale masses to the three Standard Model neutrinos, and for the first time we consider also the global fit with three sterile neutrinos. Four-neutrino oscillations of the (3+1) type have been only marginally allowed before the recent MiniBooNE results, and become even more disfavored with the new data (at the level of 4σ4\sigma). In the framework of so-called (3+2) five-neutrino mass schemes we find severe tension between appearance and disappearance experiments at the level of more than 3σ3\sigma, and hence no satistfactory fit to the global data is possible in (3+2) schemes. This tension remains also when a third sterile neutrino is added, and the quality of the global fit does not improve significantly in a (3+3) scheme. It should be noted, however, that in models with more than one sterile neutrino the MiniBooNE results are in perfect agreement with the LSND appearance evidence, thanks to the possibility of CP violation available in such oscillation schemes. Furthermore, if disappearance data are not taken into account (3+2) oscillations provide an excellent fit to the full MiniBooNE spectrum including the event excess at low energies.Comment: 30 pages, 12 figures, minor improvements of text and abstract, summary table added, matches version to be published in Phys. Rev.

    CORe50: a New Dataset and Benchmark for Continuous Object Recognition

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    Continuous/Lifelong learning of high-dimensional data streams is a challenging research problem. In fact, fully retraining models each time new data become available is infeasible, due to computational and storage issues, while na\"ive incremental strategies have been shown to suffer from catastrophic forgetting. In the context of real-world object recognition applications (e.g., robotic vision), where continuous learning is crucial, very few datasets and benchmarks are available to evaluate and compare emerging techniques. In this work we propose a new dataset and benchmark CORe50, specifically designed for continuous object recognition, and introduce baseline approaches for different continuous learning scenarios

    Top-quark decay into Higgs boson and a light quark at next-to-leading order in QCD

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    Neutral flavor-changing transitions are hugely suppressed in the Standard Model and therefore they are very sensitive to new physics. We consider the decay rate of t->u_i h where u_i=u,c using an effective field theory approach. We perform the calculation at NLO in QCD including the relevant dimension-six operators. We find that at NLO the contribution from the flavor-changing chromomagnetic operator is as important as the standard QCD correction to the flavor-changing Yukawa coupling. In addition to improving the accuracy of the theoretical predictions, the NLO calculation provides information on the operator mixing under the renormalization group.Comment: 8 pages, 5 figure

    Semi-supervised Tuning from Temporal Coherence

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    Recent works demonstrated the usefulness of temporal coherence to regularize supervised training or to learn invariant features with deep architectures. In particular, enforcing smooth output changes while presenting temporally-closed frames from video sequences, proved to be an effective strategy. In this paper we prove the efficacy of temporal coherence for semi-supervised incremental tuning. We show that a deep architecture, just mildly trained in a supervised manner, can progressively improve its classification accuracy, if exposed to video sequences of unlabeled data. The extent to which, in some cases, a semi-supervised tuning allows to improve classification accuracy (approaching the supervised one) is somewhat surprising. A number of control experiments pointed out the fundamental role of temporal coherence.Comment: Under review as a conference paper at ICLR 201
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