117 research outputs found

    Charmed quark component of the photon wave function

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    We determine the c-anti-c component of the photon wave function on the basis of (i) the data on the transitions e+ e- -> J/psi(3096), psi(3686), psi(4040), psi(4415), (ii) partial widths of the two-photon decays eta_{c0}(2979), chi_{c0}(3415), chi_{c2}(3556) -> gamma-gamma, and (iii) wave functions of the charmonium states obtained by solving the Bethe-Salpeter equation for the c-anti-c system. Using the obtained c-anti-c component of the photon wave function we calculate the gamma-gamma decay partial widths for radial excitation 2S state, eta_{c0}(3594) -> gamma-gamma, and 2P states chi_{c0}(3849), chi_{c2}(3950) -> gamma-gamma.Comment: 20 pages, 8 figure

    Quark--antiquark states and their radiative transitions in terms of the spectral integral equation. {\Huge II.} Charmonia

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    In the precedent paper of the authors (hep-ph/0510410), the bbˉb\bar b states were treated in the framework of the spectral integral equation, together with simultaneous calculations of radiative decays of the considered bottomonia. In the present paper, such a study is carried out for the charmonium (ccˉ)(c\bar c) states. We reconstruct the interaction in the ccˉc\bar c-sector on the basis of data for the charmonium levels with JPC=0+J^{PC}=0^{-+}, 11^{--}, 0++0^{++}, 1++1^{++}, 2++2^{++}, 1+1^{+-} and radiative transitions ψ(2S)γχc0(1P)\psi(2S)\to\gamma\chi_{c0}(1P), γχc1(1P)\gamma\chi_{c1}(1P), γχc2(1P)\gamma\chi_{c2}(1P), γηc(1S)\gamma\eta_{c}(1S) and χc0(1P)\chi_{c0}(1P), χc1(1P)\chi_{c1}(1P), χc2(1P)γJ/ψ\chi_{c2}(1P)\to\gamma J/\psi. The ccˉc\bar c levels and their wave functions are calculated for the radial excitations with n6n\le 6. Also, we determine the ccˉc\bar c component of the photon wave function using the e+ee^+e^- annihilation data: e+eJ/ψ(3097)e^+e^- \to J/\psi(3097), ψ(3686)\psi(3686), ψ(3770)\psi(3770), ψ(4040)\psi(4040), ψ(4160) \psi(4160), ψ(4415)\psi(4415) and perform the calculations of the partial widths of the two-photon decays for the n=1n=1 states: ηc0(1S)\eta_{c0}(1S), χc0(1P)\chi_{c0}(1P), χc2(1P)γγ\chi_{c2}(1P)\to\gamma\gamma, and n=2n=2 states: ηc0(2S)γγ\eta_{c0}(2S)\to\gamma\gamma, χc0(2P)\chi_{c0}(2P), χc2(2P)γγ\chi_{c2}(2P)\to \gamma\gamma. We discuss the status of the recently observed ccˉc\bar c states X(3872) and Y(3941): according to our results, the X(3872) can be either χc1(2P)\chi_{c1}(2P) or ηc2(1D)\eta_{c2}(1D), while Y(3941) is χc2(2P)\chi_{c2}(2P).Comment: 24 pages, 9 figure

    Quark-diquark Systematics of Baryons: Spectral Integral Equations for Systems Composed by Light Quarks

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    For baryons composed by the light quarks (q=u,dq=u,d) we write spectral integral equation using the notion of two diquarks: (i) axial--vector state, D11D^{1}_{1}, with the spin SD=1S_D=1 and isospin ID=1I_D=1 and (ii) scalar one, D00D^{0}_{0}, with the spin SD=0S_D=0 and isospin ID=0I_D=0. We present spectral integral equations for the qD00qD^{0}_{0} and qD11qD^{1}_{1} states taking into account quark--diquark confinement interaction.Comment: 13 pages, 2 figure

    The Reliability of Global and Hemispheric Surface Temperature Records

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    The purpose of this review article is to discuss the development and associated estimation of uncertainties in the global and hemispheric surface temperature records. The review begins by detailing the groups that produce surface temperature datasets. After discussing the reasons for similarities and differences between the various products, the main issues that must be addressed when deriving accurate estimates, particularly for hemispheric and global averages, are then considered. These issues are discussed in the order of their importance for temperature records at these spatial scales: biases in SST data, particularly before the 1940s; the exposure of land-based thermometers before the development of louvred screens in the late 19th century; and urbanization effects in some regions in recent decades. The homogeneity of land-based records is also discussed; however, at these large scales it is relatively unimportant. The article concludes by illustrating hemispheric and global temperature records from the four groups that produce series in near-real time

    Determination of V_cb from exclusive decays in a relativistic quark model

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    In the framework of a relativistic covariant Bethe-Salpeter model for the quark-antiquark system we present a renewed determination of the Cabbibo-Kobayashi-Maskawa matrix element Vcb|V_{cb}|. Complementing an earlier analysis applied to the whole decay spectrum for BDeνB\to D^* e\nu we now also employ the ``zero-recoil method'' that uses the end point of the decay spectrum (ω=1\omega=1) and is suited for heavy-to-heavy transitions. The averaged experimental value extracted from the data at zero recoil, VcbF(ω=1)=0.0343±0.0015|V_{cb}|{\cal F}(\omega=1)=0.0343\pm0.0015, then leads to Vcb=0.0360±0.0016|V_{cb}|=0.0360\pm 0.0016. This value is somewhat larger than the one that uses the whole decay spectrum for the model analysis. We also contrast this result to a nonrelativistic model and to recent experiments on the BDeνB\to D e\nu semileptonic decay.Comment: 7 pages, 4 figures, RevTe

    Bias adjustment and ensemble recalibration methods for seasonal forecasting: a comprehensive intercomparison using the C3S dataset

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    This work presents a comprehensive intercomparison of diferent alternatives for the calibration of seasonal forecasts, ranging from simple bias adjustment (BA)-e.g. quantile mapping-to more sophisticated ensemble recalibration (RC) methods- e.g. non-homogeneous Gaussian regression, which build on the temporal correspondence between the climate model and the corresponding observations to generate reliable predictions. To be as critical as possible, we validate the raw model and the calibrated forecasts in terms of a number of metrics which take into account diferent aspects of forecast quality (association, accuracy, discrimination and reliability). We focus on one-month lead forecasts of precipitation and temperature from four state-of-the-art seasonal forecasting systems, three of them included in the Copernicus Climate Change Service dataset (ECMWF-SEAS5, UK Met Ofce-GloSea5 and Météo France-System5) for boreal winter and summer over two illustrative regions with diferent skill characteristics (Europe and Southeast Asia). Our results indicate that both BA and RC methods efectively correct the large raw model biases, which is of paramount importance for users, particularly when directly using the climate model outputs to run impact models, or when computing climate indices depending on absolute values/thresholds. However, except for particular regions and/or seasons (typically with high skill), there is only marginal added value-with respect to the raw model outputs-beyond this bias removal. For those cases, RC methods can outperform BA ones, mostly due to an improvement in reliability. Finally, we also show that whereas an increase in the number of members only modestly afects the results obtained from calibration, longer hindcast periods lead to improved forecast quality, particularly for RC methods.This work has been funded by the C3S activity on Evaluation and Quality Control for seasonal forecasts. JMG was partially supported by the project MULTI-SDM (CGL2015-66583-R, MINECO/FEDER). FJDR was partially funded by the H2020 EUCP project (GA 776613)

    How to create an operational multi-model of seasonal forecasts?

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    Seasonal forecasts of variables like near-surface temperature or precipitation are becoming increasingly important for a wide range of stakeholders. Due to the many possibilities of recalibrating, combining, and verifying ensemble forecasts, there are ambiguities of which methods are most suitable. To address this we compare approaches how to process and verify multi-model seasonal forecasts based on a scientific assessment performed within the framework of the EU Copernicus Climate Change Service (C3S) Quality Assurance for Multi-model Seasonal Forecast Products (QA4Seas) contract C3S 51 lot 3. Our results underpin the importance of processing raw ensemble forecasts differently depending on the final forecast product needed. While ensemble forecasts benefit a lot from bias correction using climate conserving recalibration, this is not the case for the intrinsically bias adjusted multi-category probability forecasts. The same applies for multi-model combination. In this paper, we apply simple, but effective, approaches for multi-model combination of both forecast formats. Further, based on existing literature we recommend to use proper scoring rules like a sample version of the continuous ranked probability score and the ranked probability score for the verification of ensemble forecasts and multi-category probability forecasts, respectively. For a detailed global visualization of calibration as well as bias and dispersion errors, using the Chi-square decomposition of rank histograms proved to be appropriate for the analysis performed within QA4Seas.The research leading to these results is part of the Copernicus Climate Change Service (C3S) (Framework Agreement number C3S_51_Lot3_BSC), a program being implemented by the European Centre for Medium-Range Weather Forecasts (ECMWF) on behalf of the European Commission. Francisco Doblas-Reyes acknowledges the support by the H2020 EUCP project (GA 776613) and the MINECO-funded CLINSA project (CGL2017-85791-R)

    Effects of alirocumab on types of myocardial infarction: insights from the ODYSSEY OUTCOMES trial

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    Aims  The third Universal Definition of Myocardial Infarction (MI) Task Force classified MIs into five types: Type 1, spontaneous; Type 2, related to oxygen supply/demand imbalance; Type 3, fatal without ascertainment of cardiac biomarkers; Type 4, related to percutaneous coronary intervention; and Type 5, related to coronary artery bypass surgery. Low-density lipoprotein cholesterol (LDL-C) reduction with statins and proprotein convertase subtilisin–kexin Type 9 (PCSK9) inhibitors reduces risk of MI, but less is known about effects on types of MI. ODYSSEY OUTCOMES compared the PCSK9 inhibitor alirocumab with placebo in 18 924 patients with recent acute coronary syndrome (ACS) and elevated LDL-C (≥1.8 mmol/L) despite intensive statin therapy. In a pre-specified analysis, we assessed the effects of alirocumab on types of MI. Methods and results  Median follow-up was 2.8 years. Myocardial infarction types were prospectively adjudicated and classified. Of 1860 total MIs, 1223 (65.8%) were adjudicated as Type 1, 386 (20.8%) as Type 2, and 244 (13.1%) as Type 4. Few events were Type 3 (n = 2) or Type 5 (n = 5). Alirocumab reduced first MIs [hazard ratio (HR) 0.85, 95% confidence interval (CI) 0.77–0.95; P = 0.003], with reductions in both Type 1 (HR 0.87, 95% CI 0.77–0.99; P = 0.032) and Type 2 (0.77, 0.61–0.97; P = 0.025), but not Type 4 MI. Conclusion  After ACS, alirocumab added to intensive statin therapy favourably impacted on Type 1 and 2 MIs. The data indicate for the first time that a lipid-lowering therapy can attenuate the risk of Type 2 MI. Low-density lipoprotein cholesterol reduction below levels achievable with statins is an effective preventive strategy for both MI types.For complete list of authors see http://dx.doi.org/10.1093/eurheartj/ehz299</p
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