4,855 research outputs found
Doped Parton Distributions
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
, as in the massless calculation, while the DGLAP splitting functions
are those of the 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
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(). 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.
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
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 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
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 , and . 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
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
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
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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