863 research outputs found

    Rare Kaon Decays in the 1/Nc1/N_c-Expansion

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    We study the unknown coupling constants that appear at order p4p^4 in the Chiral Perturbation Theory analysis of K→πγ∗→πl+l−K \to \pi \gamma^* \to \pi l^+ l^-, K+−→π+−γγK^{+-} \to \pi^{+-} \gamma \gamma and K→ππγK \to \pi \pi \gamma decays. To that end, we compute the chiral realization of the ΔS = 1\Delta S \, = \, 1 Hamiltonian in the framework of the 1/Nc1/N_c-expansion of the low-energy action. The phenomenological implications are also discussed.Comment: 18 pages, LaTeX, CPT-92/P.279

    Text Line Segmentation of Historical Documents: a Survey

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    There is a huge amount of historical documents in libraries and in various National Archives that have not been exploited electronically. Although automatic reading of complete pages remains, in most cases, a long-term objective, tasks such as word spotting, text/image alignment, authentication and extraction of specific fields are in use today. For all these tasks, a major step is document segmentation into text lines. Because of the low quality and the complexity of these documents (background noise, artifacts due to aging, interfering lines),automatic text line segmentation remains an open research field. The objective of this paper is to present a survey of existing methods, developed during the last decade, and dedicated to documents of historical interest.Comment: 25 pages, submitted version, To appear in International Journal on Document Analysis and Recognition, On line version available at http://www.springerlink.com/content/k2813176280456k3

    Direct CP violation and the ΔI=1/2 rule in K→ππ decay from the standard model

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    We present a lattice QCD calculation of the ΔI=1/2, K→ππ decay amplitude A0 and ϵ′, the measure of direct CP violation in K→ππ decay, improving our 2015 calculation [1] of these quantities. Both calculations were performed with physical kinematics on a 323×64 lattice with an inverse lattice spacing of a-1=1.3784(68)  GeV. However, the current calculation includes nearly 4 times the statistics and numerous technical improvements allowing us to more reliably isolate the ππ ground state and more accurately relate the lattice operators to those defined in the standard model. We find Re(A0)=2.99(0.32)(0.59)×10-7  GeV and Im(A0)=-6.98(0.62)(1.44)×10-11  GeV, where the errors are statistical and systematic, respectively. The former agrees well with the experimental result Re(A0)=3.3201(18)×10-7  GeV. These results for A0 can be combined with our earlier lattice calculation of A2 [2] to obtain Re(ϵ′/ϵ)=21.7(2.6)(6.2)(5.0)×10-4, where the third error represents omitted isospin breaking effects, and Re(A0)/Re(A2)=19.9(2.3)(4.4). The first agrees well with the experimental result of Re(ϵ′/ϵ)=16.6(2.3)×10-4. A comparison of the second with the observed ratio Re(A0)/Re(A2)=22.45(6), demonstrates the standard model origin of this “ΔI=1/2 rule” enhancement.We present a lattice QCD calculation of the ΔI=1/2\Delta I=1/2, K→ππK\to\pi\pi decay amplitude A0A_0 and ε′\varepsilon', the measure of direct CP-violation in K→ππK\to\pi\pi decay, improving our 2015 calculation of these quantities. Both calculations were performed with physical kinematics on a 323×6432^3\times 64 lattice with an inverse lattice spacing of a−1=1.3784(68)a^{-1}=1.3784(68) GeV. However, the current calculation includes nearly four times the statistics and numerous technical improvements allowing us to more reliably isolate the ππ\pi\pi ground-state and more accurately relate the lattice operators to those defined in the Standard Model. We find Re(A0)=2.99(0.32)(0.59)×10−7{\rm Re}(A_0)=2.99(0.32)(0.59)\times 10^{-7} GeV and Im(A0)=−6.98(0.62)(1.44)×10−11{\rm Im}(A_0)=-6.98(0.62)(1.44)\times 10^{-11} GeV, where the errors are statistical and systematic, respectively. The former agrees well with the experimental result Re(A0)=3.3201(18)×10−7{\rm Re}(A_0)=3.3201(18)\times 10^{-7} GeV. These results for A0A_0 can be combined with our earlier lattice calculation of A2A_2 to obtain Re(ε′/ε)=21.7(2.6)(6.2)(5.0)×10−4{\rm Re}(\varepsilon'/\varepsilon)=21.7(2.6)(6.2)(5.0) \times 10^{-4}, where the third error represents omitted isospin breaking effects, and Re(A0)(A_0)/Re(A2)=19.9(2.3)(4.4)(A_2) = 19.9(2.3)(4.4). The first agrees well with the experimental result of Re(ε′/ε)=16.6(2.3)×10−4{\rm Re}(\varepsilon'/\varepsilon)=16.6(2.3)\times 10^{-4}. A comparison of the second with the observed ratio Re(A0)/(A_0)/Re(A2)=22.45(6)(A_2) = 22.45(6), demonstrates the Standard Model origin of this "ΔI=1/2\Delta I = 1/2 rule" enhancement

    Clinical consequences of nonadherence to Barrett's esophagus surveillance recommendations: a Multicenter prospective cohort study

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    Half of Barrett's esophagus (BE) surveillance endoscopies do not adhere to guideline recommendations. In this multicenter prospective cohort study, we assessed the clinical consequences of nonadherence to recommended surveillance intervals and biopsy protocol. Data from BE surveillance patients were collected from endoscopy and pathology reports; questionnaires were distributed among endoscopists. We estimated the association between (non)adherence and (i) endoscopic curability of esophageal adenocarcinoma (EAC), (ii) mortality, and (iii) misclassification of histological diagnosis according to a multistate hidden Markov model. Potential explanatory parameters (patient, facility, endoscopist variables) for nonadherence, related to clinical impact, were analyzed. In 726 BE patients, 3802 endoscopies were performed by 167 endoscopists. Adherence to surveillance interval was 16% for non-dysplastic (ND)BE, 55% for low-grade dysplasia (LGD), and 54% of endoscopies followed the Seattle protocol. There was no evidence to support the following statements: longer surveillance intervals or fewer biopsies than recommended affect endoscopic curability of EAC or cause-specific mortality (P > 0.20); insufficient biopsies affect the probability of NDBE (OR 1.0) or LGD (OR 2.3) being misclassified as high-grade dysplasia/EAC (P > 0.05). Better adherence was associated with older patients (OR 1.1), BE segments <= 2 cm (OR 8.3), visible abnormalities (OR 1.8, all P <= 0.05), endoscopists with a subspecialty (OR 3.2), and endoscopists who deemed histological diagnosis an adequate marker (OR 2.0). Clinical consequences of nonadherence to guidelines appeared to be limited with respect to endoscopic curability of EAC and mortality. This indicates that BE surveillance recommendations should be optimized to minimize the burden of endoscopies.Cellular mechanisms in basic and clinical gastroenterology and hepatolog

    Adherence to recommendations of Barrett's esophagus surveillance guidelines: A systematic review and meta-analysis

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    Background Guidelines aim to reduce treatment variation and improve quality of care. In the literature there is large variation in the reported rates of adherence to recommendations of surveillance for Barrett's esophagus (BE). The aim of this systematic review was to identify explanatory parameters determining these differences in adherence rates. Methods Embase, Medline Epub, and Web of Science were searched. Studies reporting adherence in at least one of five domains were selected: general domain, surveillance interval, biopsy protocol, landmark identification, and histopathological information. Adherence was expressed as the proportion of endoscopies or endoscopists being in accordance with guideline recommendations. Variation in adherence was evaluated by 1) meta-regression of adherence rates in random effects meta-analysis to define subgroups, and 2) compiling an overview of the most reported explanatory parameters for (non)adherence. Results 56 studies, including 14002 BE patients and 4932 endoscopists, were included. Subgroup analysis showed that variation in rates of adherences to surveillance interval recommendations (I 2 =98%-99%) was explained by difference in country (43%), by practice type (90%), and by year of publication (11%). Variation in adherence to the Seattle protocol was explained by difference in country (14%). Factors most frequently reported to be associated with better adherence were shorter BE length, salaried employment, surveillance in university hospitals, and dedicated programs. Conclusions This study provides insight into the variability of rates of adherence to BE surveillance recommendations between studies. Better adherence in university hospitals and dedi

    Climate resilience in marine protected areas and the ‘Protection Paradox’

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    Restricting human activities through Marine Protected Areas (MPAs) is assumed to create more resilient biological communities with a greater capacity to resist and recover following climate events. Here we review the evidence linking protection from local pressures (e.g., fishing and habitat destruction) with increased resilience. Despite strong theoretical underpinnings, studies have only rarely attributed resilience responses to the recovery of food webs and habitats, and increases in the diversity of communities and populations. When detected, resistance to ocean warming and recovery after extreme events in MPAs have small effect sizes against a backdrop of natural variability. By contrast, large die-offs are well described from MPAs following climate stress events. This may be in part because protection from one set of pressures or drivers (such as fishing) can select for species that are highly sensitive to others (such as warming), creating a ‘Protection Paradox’. Given that climate change is overwhelming the resilience capacity of marine ecosystems, the only primary solution is to reduce carbon emissions. High-quality monitoring data in both space and time can also identify emergent resilience signals that do exist, in combination with adequate reference data to quantify the initial system state. This knowledge will allow networks of diverse protected areas to incorporate spatial refugia against climate change, and identify resilient biological components of natural systems. Sufficient spatial replication further offers insurance against losses in any given MPA, and the possibility for many weak signals of resilience to accumulate

    Heavy quarkonium: progress, puzzles, and opportunities

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    A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the BB-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair

    Understanding How Inequality in the Distribution of Income Affects Health

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    Research on the determinants of health has almost exclusively focused on the individual but it seems clear we cannot understand or improve patterns of population health without engaging structural determinants at the societal level. This article traces the development of research on income distribution and health to the most recent epidemiologic studies from the USA that show how income inequality is related to age-adjusted mortality within the 50 States. (r 520.62, p 5 0.0001) even after accounting for absolute levels of income. We discuss potential material, psychological, social and behavioral pathways through which income distribution might be linked to health status. Distributional aspects of the economy are important determinants of health and may well provide one of the most pertinent indicators of overall social well-being.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66686/2/10.1177_135910539700200303.pd

    Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

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    Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
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