4,855 research outputs found

    Doped Parton Distributions

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    Calculations of high-energy processes involving the production of b-quarks are typically performed in two different ways, the massive four-flavour scheme (4FS) and the massless five-flavour scheme (5FS). For processes where the combination of the 4FS and 5FS results into a matched calculation is technically difficult, it is possible to define a hybrid scheme known as the doped scheme, where above the b-quark threshold the strong coupling runs with nf=5n_f=5, as in the massless calculation, while the DGLAP splitting functions are those of the nf=4n_f=4 scheme. In this contribution we present NNPDF3.0 PDF sets in this doped scheme, compare them with the corresponding 4FS and 5FS sets, and discuss their relevance for LHC phenomenology.Comment: 5 pages, 5 figures, to appear in the proceedings of the 27th Rencontres de Blois on Particle Physics and Cosmology, Blois, May 31 to June 05, 201

    APFEL: A PDF Evolution Library with QED corrections

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    Quantum electrodynamics and electroweak corrections are important ingredients for many theoretical predictions at the LHC. This paper documents APFEL, a new PDF evolution package that allows for the first time to perform DGLAP evolution up to NNLO in QCD and to LO in QED, in the variable-flavor-number scheme and with either pole or MSbar heavy quark masses. APFEL consistently accounts for the QED corrections to the evolution of quark and gluon PDFs and for the contribution from the photon PDF in the proton. The coupled QCD+QED equations are solved in x-space by means of higher order interpolation, followed by Runge-Kutta solution of the resulting discretized evolution equations. APFEL is based on an innovative and flexible methodology for the sequential solution of the QCD and QED evolution equations and their combination. In addition to PDF evolution, APFEL provides a module that computes Deep-Inelastic Scattering structure functions in the FONLL general-mass variable-flavor-number scheme up to O(αs2\alpha_s^2). All the functionalities of APFEL can be accessed via a Graphical User Interface, supplemented with a variety of plotting tools for PDFs, parton luminosities and structure functions. Written in Fortran 77, APFEL can also be used via the C/C++ and Python interfaces, and is publicly available from the HepForge repository.Comment: 34 pages, 5 figures. Final version, to be published in CPC. Several corrections and improvements. Program available from http://apfel.hepforge.org

    Effects of non-pharmacological or pharmacological interventions on cognition and brain plasticity of aging individuals.

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    Brain aging and aging-related neurodegenerative disorders are major health challenges faced by modern societies. Brain aging is associated with cognitive and functional decline and represents the favourable background for the onset and development of dementia. Brain aging is associated with early and subtle anatomo-functional physiological changes that often precede the appearance of clinical signs of cognitive decline. Neuroimaging approaches unveiled the functional correlates of these alterations and helped in the identification of therapeutic targets that can be potentially useful in counteracting age-dependent cognitive decline. A growing body of evidence supports the notion that cognitive stimulation and aerobic training can preserve and enhance operational skills in elderly individuals as well as reduce the incidence of dementia. This review aims at providing an extensive and critical overview of the most recent data that support the efficacy of non-pharmacological and pharmacological interventions aimed at enhancing cognition and brain plasticity in healthy elderly individuals as well as delaying the cognitive decline associated with dementia

    APFELgrid: a high performance tool for parton density determinations

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    We present a new software package designed to reduce the computational burden of hadron collider measurements in Parton Distribution Function (PDF) fits. The APFELgrid package converts interpolated weight tables provided by APPLgrid files into a more efficient format for PDF fitting by the combination with PDF and αs\alpha_s evolution factors provided by APFEL. This combination significantly reduces the number of operations required to perform the calculation of hadronic observables in PDF fits and simplifies the structure of the calculation into a readily optimised scalar product. We demonstrate that our technique can lead to a substantial speed improvement when compared to existing methods without any reduction in numerical accuracy.Comment: 13 pages, 2 figures. Submitted to CPC. Code available from https://github.com/nhartland/APFELgri

    On the Impact of Lepton PDFs

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    In this paper we discuss the effect of the complete leading-order QED corrections to the DGLAP equations in the perturbative evolution of parton distribution functions (PDFs). This requires the extension of the purely QCD DGLAP evolution, including a PDF for the photons and, consistently, also for the charged leptons e±e^{\pm}, μ±\mu^\pm and τ±\tau^\pm. We present the implementation of the QED-corrected DGLAP evolution in the presence of photon and lepton PDFs in the APFEL program and, by means of different assumptions for the initial scale PDFs, we produce for the first time PDF sets containing charged lepton distributions. We also present phenomenological studies that aim to assess the impact of the presence of lepton PDFs in the proton for some relevant SM (and BSM) processes at the LHC at 13 TeV and the FCC-hh at 100 TeV. The impact of the photon PDF is also outlined for those processes.Comment: 32 pages, 19 figures, matches published version in JHE

    School catering supply chains: study on 5 cases

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    This study presents accurate data on the school catering systems of five different municipalities which decided to invest on service quality and sustainable development. The aim is to provide a compendium to be considered by other local authorities and then used as an educational tool for drafting new templates for tender specifications. Regional laws as drivers for promoting organic consumption in school canteens and waste reduction through self service systems are two examples of interesting models for sustainable school food catering. This work does not present a unique best practice model but constellations of reference models for each different situation: in such way each municipality can consult the most fit case study and search the best solution according to specific variables

    Main constraints in developing public organic procurement

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    The present study investigates how to increase and improve school catering supply chains, to understand hindering factors and their perception in order to reveal drivers and constraints for POP. These include policy implementation instruments, changed values and attitudes, healthy nutrition policies, supply chain bottle necks, premium prices (to producers), successful procurement strategies and certification procedures. This work is based on a two-step survey concerning the Italian school food service system. Initially questionnaires were submitted to a qualified group of 50 producers and 50 caterers (managers of national and international companies of food service for school, local administrators who manage food services for the schools). The results of the questionnaires have subsequently been the basis to plan in-depth interviews with few decision makers who could represent both caterers and producers. The aim of this second step being to view how identified problems could be solved. The results show how the understanding and the acceptance of the organic food concept among the catering staff is crucial for the degree of success in each step of public organic procurement. The introduction of organic food in serving outlets needs appropriate support (such as qualification of key actors and a specific financial support). Other key aspects in this regard are laws and regulations promoting the procurement of quality food, policy interventions tackling more than one aspect of the problem, education programs, calls for tenders, negotiated procurement contracts and quality standards

    Organising supply chains of organic products for Italian school meals - The case of the province and of the city of Piacenza

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    The paper is part of the proceedings of an iPOPY seminar. The authors describe, how supply chains of organic school food might be organised in a sustainable way in order to serve high quality food to pupils. They present a best practice case of controlled food chains (filiera controllata) from Italy, the European champion of organic school food. From the province and the city of Piacenza in the region of Emilia-Romagna, we can learn a lot about a short and certified organic food-chain, a wide range of regional and organic products provided through a shared logistic organisation among local partners, and specific tender procedures
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