1,071 research outputs found

    Charmonium properties from lattice QCD + QED: hyperfine splitting, J/ψJ/\psi leptonic width, charm quark mass and aμca_{\mu}^c

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    We have performed the first nf=2+1+1n_f = 2+1+1 lattice QCD computations of the properties (masses and decay constants) of ground-state charmonium mesons. Our calculation uses the HISQ action to generate quark-line connected two-point correlation functions on MILC gluon field configurations that include u/du/d quark masses going down to the physical point, tuning the cc quark mass from MJ/ψM_{J/\psi} and including the effect of the cc quark's electric charge through quenched QED. We obtain MJ/ψMηcM_{J/\psi}-M_{\eta_c} (connected) = 120.3(1.1) MeV and interpret the difference with experiment as the impact on MηcM_{\eta_c} of its decay to gluons, missing from the lattice calculation. This allows us to determine ΔMηcannihiln\Delta M_{\eta_c}^{\mathrm{annihiln}} =+7.3(1.2) MeV, giving its value for the first time. Our result of fJ/ψ=f_{J/\psi}= 0.4104(17) GeV, gives Γ(J/ψe+e)\Gamma(J/\psi \rightarrow e^+e^-)=5.637(49) keV, in agreement with, but now more accurate than experiment. At the same time we have improved the determination of the cc quark mass, including the impact of quenched QED to give mc(3GeV)\overline{m}_c(3\,\mathrm{GeV}) = 0.9841(51) GeV. We have also used the time-moments of the vector charmonium current-current correlators to improve the lattice QCD result for the cc quark HVP contribution to the anomalous magnetic moment of the muon. We obtain aμc=14.638(47)×1010a_{\mu}^c = 14.638(47) \times 10^{-10}, which is 2.5σ\sigma higher than the value derived using moments extracted from some sets of experimental data on R(e+ehadrons)R(e^+e^- \rightarrow \mathrm{hadrons}). This value for aμca_{\mu}^c includes our determination of the effect of QED on this quantity, δaμc=0.0313(28)×1010\delta a_{\mu}^c = 0.0313(28) \times 10^{-10}.Comment: Added extra discussion on QED setup, some new results to study the effects of strong isospin breaking in the sea (including new Fig. 1) and a fit stability plot for the hyperfine splitting (new Fig. 7). Version accepted for publication in PR

    BKB_K using HYP-smeared staggered fermions in Nf=2+1N_f=2+1 unquenched QCD

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    We present results for kaon mixing parameter BKB_K calculated using HYP-smeared improved staggered fermions on the MILC asqtad lattices. We use three lattice spacings (a0.12a\approx 0.12, 0.090.09 and 0.06  0.06\;fm), ten different valence quark masses (mms/10msm\approx m_s/10-m_s), and several light sea-quark masses in order to control the continuum and chiral extrapolations. We derive the next-to-leading order staggered chiral perturbation theory (SChPT) results necessary to fit our data, and use these results to do extrapolations based both on SU(2) and SU(3) SChPT. The SU(2) fitting is particularly straightforward because parameters related to taste-breaking and matching errors appear only at next-to-next-to-leading order. We match to the continuum renormalization scheme (NDR) using one-loop perturbation theory. Our final result is from the SU(2) analysis, with the SU(3) result providing a (less accurate) cross check. We find BK(NDR,μ=2GeV)=0.529±0.009±0.032B_K(\text{NDR}, \mu = 2 \text{GeV}) = 0.529 \pm 0.009 \pm 0.032 and B^K=BK(RGI)=0.724±0.012±0.043\hat{B}_K =B_K(\text{RGI})= 0.724 \pm 0.012 \pm 0.043, where the first error is statistical and the second systematic. The error is dominated by the truncation error in the matching factor. Our results are consistent with those obtained using valence domain-wall fermions on lattices generated with asqtad or domain-wall sea quarks.Comment: 37 pages, 31 figures, most updated versio

    Prioritization of fish communities with a view to conservation and restoration on a large scale European basin, the Loire (France)

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    The hierarchical organization of important sites for the conservation or the restoration of fish communities is a great challenge for managers, especially because of financial or time constraints. In this perspective, we developed a methodology, which is easy to implement in different locations. Based on the fish assemblage characteristics of the Loire basin (France), we created a synthetic conservation value index including the rarity, the conservation status and the species origin. The relationship between this new synthetic index and the Fish-Based Index allowed us to establish a classification protocol of the sites along the Loire including fish assemblages to be restored or conserved. Sites presenting disturbed fish assemblages, a low rarity index, few threatened species, and a high proportion of non-native species were considered as important for the restoration of fish biodiversity. These sites were found mainly in areas where the assemblages are typical of the bream zone, e.g. with a higher number of eurytopic and limnophilic species. On the contrary, important sites for conservation were defined as having an important conservation potential (high RI, a lot of threatened species, and few nonnatives fish species) and an undisturbed fish assemblage similar to the expected community if habitats are undisturbed. Important sites for conservation were found in the Loire basin’s medium reaches which host assemblages typical for the grayling and the barbell zones, e.g. with a higher number of rheophilic species. The synthetic conservation value index could be adapted and completed with other criteria according to management priorities and capacities

    The Glial Regenerative Response to Central Nervous System Injury Is Enabled by Pros-Notch and Pros-NFκB Feedback

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    Organisms are structurally robust, as cells accommodate changes preserving structural integrity and function. The molecular mechanisms underlying structural robustness and plasticity are poorly understood, but can be investigated by probing how cells respond to injury. Injury to the CNS induces proliferation of enwrapping glia, leading to axonal re-enwrapment and partial functional recovery. This glial regenerative response is found across species, and may reflect a common underlying genetic mechanism. Here, we show that injury to the Drosophila larval CNS induces glial proliferation, and we uncover a gene network controlling this response. It consists of the mutual maintenance between the cell cycle inhibitor Prospero (Pros) and the cell cycle activators Notch and NFκB. Together they maintain glia in the brink of dividing, they enable glial proliferation following injury, and subsequently they exert negative feedback on cell division restoring cell cycle arrest. Pros also promotes glial differentiation, resolving vacuolization, enabling debris clearance and axonal enwrapment. Disruption of this gene network prevents repair and induces tumourigenesis. Using wound area measurements across genotypes and time-lapse recordings we show that when glial proliferation and glial differentiation are abolished, both the size of the glial wound and neuropile vacuolization increase. When glial proliferation and differentiation are enabled, glial wound size decreases and injury-induced apoptosis and vacuolization are prevented. The uncovered gene network promotes regeneration of the glial lesion and neuropile repair. In the unharmed animal, it is most likely a homeostatic mechanism for structural robustness. This gene network may be of relevance to mammalian glia to promote repair upon CNS injury or disease

    Parametric Modeling Investigation of a Radially-Staged Low-Emission Aviation Combustor

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    Aviation gas-turbine combustion demands high efficiency, wide operability and minimal trace gas emissions. Performance critical design parameters include injector geometry, combustor layout, fuel-air mixing and engine cycle conditions. The present investigation explores these factors and their impact on a radially staged low-emission aviation combustor sized for a next-generation 24,000-lbf-thrust engine. By coupling multi-fidelity computational tools, a design exploration was performed using a parameterized annular combustor sector at projected 100% takeoff power conditions. Design objectives included nitrogen oxide emission indices and overall combustor pressure loss. From the design space, an optimal configuration was selected and simulated at 7.1, 30 and 85% part-power operation, corresponding to landing-takeoff cycle idle, approach and climb segments. All results were obtained by solution of the steady-state Reynolds-averaged Navier-Stokes equations. Species concentrations were solved directly using a reduced 19-step reaction mechanism for Jet-A. Turbulence closure was obtained using a nonlinear K-epsilon model. This research demonstrates revolutionary combustor design exploration enabled by multi-fidelity physics-based simulation

    Profiling adult literacy facilitators in development contexts: An ethnographic study in Ethiopia

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    Teachers/facilitators in adult literacy learning programmes are recognised as being vital to successful learning outcomes. But little is known about them as a group. This small-scale research project comprising ethnographic-style case studies of five adult literacy facilitators (ALFs) in Ethiopia seeks to throw some light on these teachers, their backgrounds and what they bring to their teaching, with a view to improving the effectiveness of their work. The researchers found that all of the ALFs had high levels of commitment, but none of the ALFs received much in the way of training, and professional support for their role was in some cases missing. The degree (and their perception) of their own literacy practices varied greatly among them, even in their common use of mobile phones. It also emerged that while they had all fought very hard for their own education, one of the main reasons all of them stated for going into literacy teaching was not a general belief in the value of education but their priority need of a regular income. Another insight is that the female ALFs struggled more than their male counterparts in engaging learners; the women were criticised more excessively than the men. This research reveals something of the diversity of facilitators, and concludes that further such studies are needed in different contexts

    Current concepts of the management of dental extractions for patients taking warfarin

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    The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.Background: Controversy has surrounded the correct management of patients therapeutically anticoagulated with warfarin who require dental extractions. The risk of bleeding must be weighed up against the risk of thromboembolism when deciding whether to interfere with a patient's warfarin regimen. An improved understanding of the importance of fibrinolytic mechanisms in the oral cavity has resulted in the development of various local measures to enable these patients to be treated on an outpatient basis. Methods: A review of the literature was undertaken. This was supplemented by the authors' clinical trials and extensive clinical experience with anticoagulated patients. Results: Various protocols for treating patients taking warfarin have been reviewed and summarized and an overview of the haemostatic and fibrinolytic systems is presented. A protocol for management of warfarinized patients requiring dental extractions in the outpatient setting is proposed. Conclusions: Patients therapeutically anticoagulated with warfarin can be treated on an ambulatory basis, without interruption of their warfarin regimen provided appropriate local measures are used.G Carter, AN Goss, JV Lloyd, R Tocchett
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