779 research outputs found

    ππ\pi\pi scattering S wave from the data on the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n

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    The results of the recent experiments on the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 ππ\pi\pi S wave phase shift δ00\delta^0_0 and inelasticity η00\eta^0_0 a new set of data is obtained. Difficulties emerging when using the physical solutions for the π0π0\pi^0\pi^0 S and D wave amplitudes extracted with the partial wave analyses are discussed. Attention is drawn to the fact that, for the π0π0\pi^0\pi^0 invariant mass, m, above 1 GeV, the other solutions, in principle, are found to be more preferred. For clarifying the situation and further studying the f0(980)f_0(980) resonance thorough experimental investigations of the reaction πpπ0π0n\pi^-p\to\pi^0\pi^0n in the m region near the KKˉK\bar K threshold are required.Comment: 17 pages, 5 figure

    A low-lying scalar meson nonet in a unitarized meson model

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    A unitarized nonrelativistic meson model which is successful for the description of the heavy and light vector and pseudoscalar mesons yields, in its extension to the scalar mesons but for the same model parameters, a complete nonet below 1 GeV. In the unitarization scheme, real and virtual meson-meson decay channels are coupled to the quark-antiquark confinement channels. The flavor-dependent harmonic-oscillator confining potential itself has bound states epsilon(1.3 GeV), S(1.5 GeV), delta(1.3 GeV), kappa(1.4 GeV), similar to the results of other bound-state qqbar models. However, the full coupled-channel equations show poles at epsilon(0.5 GeV), S(0.99 GeV), delta(0.97 GeV), kappa(0.73 GeV). Not only can these pole positions be calculated in our model, but also cross sections and phase shifts in the meson-scattering channels, which are in reasonable agreement with the available data for pion-pion, eta-pion and Kaon-pion in S-wave scattering.Comment: A slightly revised version of Zeitschrift fuer Physik C30, 615 (1986

    An agenda for ethics and justice in adaptation to climate change

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    As experts predict that at least some irreversible climate change will occur with potentially disastrous effects on the lives and well-being of vulnerable communities around the world, it is paramount to ensure that these communities are resilient and have adaptive capacity to withstand the consequences. Adaptation and resilience planning present several ethical issues that need to be resolved if we are to achieve successful adaptation and resilience to climate change, taking into consideration vulnerabilities and inequalities in terms of power, income, gender, age, sexuality, race, culture, religion, and spatiality. Sustainable adaptation and resilience planning that addresses these ethical issues requires interdisciplinary dialogues between the natural sciences, social sciences, and philosophy, in order to integrate empirical insights on socioeconomic inequality and climate vulnerability with ethical analysis of the underlying causes and consequences of injustice in adaptation and resilience. In this paper, we set out an interdisciplinary research agenda for the inclusion of ethics and justice theories in adaptation and resilience planning, particularly into the Sixth Assessment Report of the International Panel on Climate Change (IPCC AR6). We present six core discussions that we believe should be an integral part of these interdisciplinary dialogues on adaptation and resilience as part of IPCC AR6, especially Chapters 2 (“Terrestial and freshwater ecosystems and their services”), 6 (“Cities, settlements and key infrastructure”), 7 (“Health, wellbeing and the changing structure of communities”), 8 (“Poverty, livelihoods and sustainable development”), 16 “Key risks across sectors and regions”), 17 (“Decision-making options for managing risk”), and 18 (“Climate resilient development pathways”).: (i) Where does ‘justice’ feature in resilience and adaptation planning and what does it require in that regard?; (ii) How can it be ensured that adaptation and resilience strategies protect and take into consideration and represent the interest of the most vulnerable women and men, and communities?; (iii) How can different forms of knowledge be integrated within adaptation and resilience planning?; (iv) What trade-offs need to be made when focusing on resilience and adaptation and how can they be resolved?; (v) What roles and responsibilities do different actors have to build resilience and achieve adaptation?; (vi) Finally, what does the focus on ethics imply for the practice of adaptation and resilience planning

    Another look at ππ\pi\pi scattering in the scalar channel

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    We set up a general framework to describe ππ\pi\pi scattering below 1 GeV based on chiral low-energy expansion with possible spin-0 and 1 resonances. Partial wave amplitudes are obtained with the N/DN/D method, which satisfy unitarity, analyticity and approximate crossing symmetry. Comparison with the phase shift data in the J=0 channel favors a scalar resonance near the ρ\rho mass.Comment: 17 pages, 5 figures, REVTe

    Personalised service? Changing the role of the government librarian

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    Investigates the feasibility of personalised information service in a government department. A qualitative methodology explored stakeholder opinions on the remit, marketing, resourcing and measurement of the service. A questionnaire and interviews gathered experiences of personalised provision across the government sector. Potential users were similarly surveyed to discuss how the service could meet their needs. Data were analysed using coding techniques to identify emerging theory. Lessons learned from government librarians centred on clarifying requirements, balancing workloads and selective marketing. The user survey showed low usage and awareness of existing specialist services, but high levels of need and interest in services repackaged as a tailored offering. Fieldwork confirmed findings from the literature on the scope for adding value through information management advice, information skills training and substantive research assistance and the need to understand business processes and develop effective partnerships. Concluding recommendations focus on service definition, strategic marketing, resource utilisation and performance measurement

    What is the structure of the Roper resonance?

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    We investigate the structure of the nucleon resonance N^*(1440) (Roper) within a coupled-channel meson exchange model for pion-nucleon scattering. The coupling to pipiN states is realized effectively by the coupling to the sigmaN, piDelta and rhoN channels. The interaction within and between these channels is derived from an effective Lagrangian based on a chirally symmetric Lagrangian, which is supplemented by well known terms for the coupling of the Delta isobar, the omega meson and the 'sigma', which is the name given here to the strong correlation of two pions in the scalar-isoscalar channel. In this model the Roper resonance can be described by meson-baryon dynamics alone; no genuine N^*(1440) (3 quark) resonance is needed in order to fit piN phase shifts and inelasticities.Comment: 55 pages, 14 figure

    Combined multiplex panel test results are a poor estimate of disease prevalence without adjustment for test error

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    This is the uncorrected proof.Data Availability: All data and code used for running experiments, model fitting, and plotting is available on a GitHub repository at https://bristol-vaccine-centre.github.io/testerror/. This is in the form of an R package providing methods to support the estimation of epidemiological parameters based on the results of multiplex panel tests and it is deployed on the Bristol Vaccine Centre r-universe (https://bristol-vaccine-centre.r-universe.dev/testerror). We have also used Zenodo to assign a DOI to the repository: doi:10.5281/zenodo.7691196.Multiplex panel tests identify many individual pathogens at once, using a set of component tests. In some panels the number of components can be large. If the panel is detecting causative pathogens for a single syndrome or disease then we might estimate the burden of that disease by combining the results of the panel, for example determining the prevalence of pneumococcal pneumonia as caused by many individual pneumococcal serotypes. When we are dealing with multiplex test panels with many components, test error in the individual components of a panel, even when present at very low levels, can cause significant overall error. Uncertainty in the sensitivity and specificity of the individual tests, and statistical fluctuations in the numbers of false positives and false negatives, will cause large uncertainty in the combined estimates of disease prevalence. In many cases this can be a source of significant bias. In this paper we develop a mathematical framework to characterise this issue, we determine expressions for the sensitivity and specificity of panel tests. In this we identify a counter-intuitive relationship between panel test sensitivity and disease prevalence that means panel tests become more sensitive as prevalence increases. We present novel statistical methods that adjust for bias and quantify uncertainty in prevalence estimates from panel tests, and use simulations to test these methods. As multiplex testing becomes more commonly used for screening in routine clinical practice, accumulation of test error due to the combination of large numbers of test results needs to be identified and corrected for.Engineering and Physical Sciences Research Council (EPSRC)Medical Research Council (MRC)National Institute for Health and Care Research (NIHR

    Couplings of light I=0 scalar mesons to simple operators in the complex plane

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    The flavour and glue structure of the light scalar mesons in QCD are probed by studying the couplings of the I=0 mesons σ(600)\sigma(600) and f0(980)f_0(980) to the operators qˉq\bar{q}q, αsG2\alpha_s G^2 and to two photons. The Roy dispersive representation for the ππ\pi\pi amplitude t00(s)t_0^0(s) is used to determine the pole positions as well as the residues in the complex plane. On the real axis, t00t_0^0 is constrained to solve the Roy equation together with elastic unitarity up to the K\Kbar threshold leading to an improved description of the f0(980)f_0(980). The problem of using a two-particle threshold as a matching point is discussed. A simple relation is established between the coupling of a scalar meson to an operator jSj_S and the value of the related pion form-factor computed at the resonance pole. Pion scalar form-factors as well as two-photon partial-wave amplitudes are expressed as coupled-channel Omn\`es dispersive representations. Subtraction constants are constrained by chiral symmetry and experimental data. Comparison of our results for the qˉq\bar{q}q couplings with earlier determinations of the analogous couplings of the lightest I=1 and I=1/2I=1/2 scalar mesons are compatible with an assignment of the σ\sigma, κ\kappa, a0(980)a_0(980), f0(980)f_0(980) into a nonet. Concerning the gluonic operator αsG2\alpha_s G^2 we find a significant coupling to both the σ\sigma and the f0(980)f_0(980).Comment: 31 pages, 5 figure
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