245 research outputs found
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
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
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
On the GRAIL-LLR Low-Degree Gravity Field Inconsistencies
No abstract availabl
Angular correlations in the cosmic gamma-ray background from dark matter annihilation around intermediate-mass black holes
Dark matter (DM) annihilation could in principle contribute to the diffuse
cosmic gamma-ray back- ground (CGB). While with standard assumptions for
cosmological and particle physics parameters this contribution is expected to
be rather small, a number of processes could boost it, including a
larger-than-expected DM annihilation cross-section, or the occurance of DM
substructures such as DM mini-spikes around intermediate-mass black holes. We
show that angular correlations of the CGB provide a tool to disentangle the
signal induced by DM annihilation in mini-spikes from a conventional
astrophysical component. Treating blazars as a known background, we study the
prospects for detecting DM annihilations with the Fermi Gamma-Ray Space
Telescope for different choices of DM mass and annihilation channels.Comment: 13 pages, 11 figure
A determination of the fragmentation functions of pions, kaons, and protons with faithful uncertainties
We present NNFF1.0, a new determination of the fragmentation functions (FFs)
of charged pions, charged kaons, and protons/antiprotons from an analysis of
single-inclusive hadron production data in electron-positron annihilation. This
determination, performed at leading, next-to-leading, and
next-to-next-to-leading order in perturbative QCD, is based on the NNPDF
methodology, a fitting framework designed to provide a statistically sound
representation of FF uncertainties and to minimise any procedural bias. We
discuss novel aspects of the methodology used in this analysis, namely an
optimised parametrisation of FFs and a more efficient minimisation
strategy, and validate the FF fitting procedure by means of closure tests. We
then present the NNFF1.0 sets, and discuss their fit quality, their
perturbative convergence, and their stability upon variations of the kinematic
cuts and the fitted dataset. We find that the systematic inclusion of
higher-order QCD corrections significantly improves the description of the
data, especially in the small- region. We compare the NNFF1.0 sets to other
recent sets of FFs, finding in general a reasonable agreement, but also
important differences. Together with existing sets of unpolarised and polarised
parton distribution functions (PDFs), FFs and PDFs are now available from a
common fitting framework for the first time.Comment: 50 pages, 22 figures, 5 table
Modifica delle caratteristiche superficiali dell'ABS mediante rivestimenti isolanti per stampi a iniezione
In questa tesi si indagano gli effetti che l'uso di un rivestimento in DLC (diamond-like-carbon) causa sulla morfologia della fase dispersa nell'ABS. Non sono stati riscontrati effetti diversi da quelli causati da stampo convenzionale nei riguardi della deformazione del butadiene in superficie. Si è però riscontrato come i coatings rallentino un fenomeno migratorio.ope
Time Transfer functions as a way to validate light propagation solutions for space astrometry
Given the extreme accuracy of modern space astrometry, a precise relativistic
modeling of observations is required. Concerning light propagation, the
standard procedure is the solution of the null-geodesic equations. However,
another approach based on the Time Transfer Functions (TTF) has demonstrated
its capability to give access to key quantities such as the time of flight of a
light signal between two point-events and the tangent vector to its
null-geodesic in a weak gravitational field using an integral-based method. The
availability of several models, formulated in different and independent ways,
must not be considered like an oversized relativistic toolbox. Quite the
contrary, they are needed as validation to put future experimental results on
solid ground. The objective of this work is then twofold. First, we build the
time of flight and tangent vectors in a closed form within the TTF formalism
giving the case of a time dependent metric. Second, we show how to use this new
approach to obtain a comparison of the TTF with two existing modelings, namely
GREM and RAMOD. In this way, we evidentiate the mutual consistency of the three
models, opening the basis for further links between all the approaches, which
is mandatory for the interpretation of future space missions data. This will be
illustrated through two recognized cases: a static gravitational field and a
system of monopoles in uniform motion.Comment: 16 pages, submitted to CQ
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