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Resultados filtrados por Publicador: Universidade Cornell

## aMCfast: automation of fast NLO computations for PDF fits

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/06/2014
Português

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We present the interface between MadGraph5_aMC@NLO, a self-contained program
that calculates cross sections up to next-to-leading order accuracy in an
automated manner, and APPLgrid, a code that parametrises such cross sections in
the form of look-up tables which can be used for the fast computations needed
in the context of PDF fits. The main characteristic of this interface, which we
dub aMCfast, is its being fully automated as well, which removes the need to
extract manually the process-specific information for additional physics
processes, as is the case with other matrix element calculators, and renders it
straightforward to include any new process in the PDF fits. We demonstrate this
by studying several cases which are easily measured at the LHC, have a good
constraining power on PDFs, and some of which were previously unavailable in
the form of a fast interface.; Comment: 36 pages, 10 figures

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## Theoretical model to deduce a PDF with a power law tail using Extreme Physical Information

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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#Physics - Data Analysis, Statistics and Probability#Nonlinear Sciences - Adaptation and Self-Organizing Systems

The theory of Extreme Physical Information (EPI) is used to deduce a
probability density function (PDF) of a system that exhibits a power law tail.
The computed PDF is useful to study and fit several observed distributions in
complex systems. With this new approach it is possible to describe extreme and
rare events in the tail, and also the frequent events in the distribution head.
Using EPI, an information functional is constructed, and minimized using
Euler-Lagrange equations. As a solution, a second order differential equation
is derived. By solving this equation a family of functions is calculated. Using
these functions it is possible to describe the system in terms of eigenstates.
A dissipative term is introduced into the model, as a relevant term for the
study of open systems. One of the main results is a mathematical relation
between the scaling parameter of the power law observed in the tail and the
shape of the head.; Comment: 11 pages, 12 figures, 1 table, 2 appendices

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## Nuclear PDF constraints from p+Pb collisions at the LHC

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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As the current nuclear PDF analyses are mainly constrained by fixed-target
Drell-Yan and deeply inelastic scattering data only the quark nuclear
modifications at fairly large $x$ values are in a good control. Inclusive pion
production in d+Au collisions at RHIC provides some constraints for gluons but
due to the limited kinematic reach of the data the gluon modifications remain
uncertain especially at small values of $x$. In this talk, we discuss how the
existing data from p+Pb collisions at the LHC can improve the nuclear PDF fits
and which measurements would be sensitive to the small-$x$ gluons. In
particular, we consider inclusive hadron production, compare this to direct
photons, and show estimates of the effect of CMS dijet measurements to the
uncertainty of nuclear gluon distributions.; Comment: Talk presented at DIS2015 conference, April 27 - May 1, 2015,
Southern Methodist University, Dallas, Texas. v2: updated reference list

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## PDF uncertainties in the determination of the W boson mass and of the effective lepton mixing angle at the LHC

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 21/05/2013
Português

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The precision measurement of the W boson mass allows to perform stringent
consistency tests of the Standard Model by means of global electroweak fits.
The accurate determination of the W boson mass is one of the legacy results of
the Tevatron, where the experimental accuracy is such that $M_W$ is now limited
by theoretical uncertainties related to the parton distributions of the proton.
In this contribution, we show how to quantify the impact of PDF uncertainties
in the measurement of $M_W$ at the Tevatron and the LHC by means of a template
method, and study both the use of the W transverse mass and the lepton pT
kinematical distributions to generate these templates. We also present
preliminary results on the quantification of the PDF uncertainties in the
determination of the effective lepton mixing angle at the LHC, based on the
same template method as for the W mass determination; Comment: 5 pages, 4 figures, to appear in the proceedings of the XXI
International Workshop on Deep-Inelastic Scattering and Related Subjects
(DIS2013), Marseille, 22-26 April 2013

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## Charm and beauty quark masses in the MMHT2014 global PDF analysis

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 08/10/2015
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We investigate the variation in the MMHT2014 PDFs when we allow the heavy
quark masses $m_c$ and $m_b$ to vary away from their default values. We make
PDF sets available in steps of $\Delta m_c =0.05~{\rm GeV}$ and $\Delta m_b
=0.25~{\rm GeV}$, and present the variation in the PDFs and in the predictions.
We examine the comparison to the HERA data on charm and beauty structure
functions and note that in each case the heavy quark data, and the inclusive
data, have a slight preference for lower masses than our default values. We
provide PDF sets with 3 and 4 active quark flavours, as well as the standard
value of 5 flavours. We use the pole mass definition of the quark masses, as in
the default MMHT2014 analysis, but briefly comment on the $\overline{\rm MS}$
definition.; Comment: 20 pages, 12 figures

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## PDF uncertainties in the extraction of the W mass at LHC: a Snowmass Whitepaper

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 05/09/2013
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The precision measurement of the W boson mass is an important milestone for
the LHC physics program in the coming years. An accurate measurement of $M_W$
allows to perform stringent consistency tests of the Standard Model by means of
global electroweak fits, which in turn are sensitive to New Physics at scales
potentially higher than the ones explored in direct searches. From the
theoretical point of view, our limited knowledge of PDFs will be one of the
dominant sources of uncertainty in ongoing and future LHC determinations of
$M_W$. In this whitepaper, we have quantified the impact of PDF uncertainties
in the W mass extractions from the transverse mass distribution at the LHC. The
calculation has been performed using the NNPDF2.3 set, which includes direct
constrains on the W boson production kinematics with data for electroweak gauge
boson production from the LHC. Our results confirm previous estimates that PDF
uncertainties in the determination of $M_W$ from the $m_W^T$ distribution are
moderate, around 10 MeV at most. We briefly discuss also the case of the lepton
$p_T$ distribution.; Comment: 6 pages, 4 figures, contribution to Snowmass 2013

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## PDF/A standard for long term archiving

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 04/06/2009
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PDF/A is defined by ISO 19005-1 as a file format based on PDF format. The
standard provides a mechanism for representing electronic documents in a way
that preserves their visual appearance over time, independent of the tools and
systems used for creating or storing the files.; Comment: 8 pages, exposed on 5th International Conference "Actualities and
Perspectives on Hardware and Software" - APHS2009, Timisoara, Romania

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## Reengineering PDF-Based Documents Targeting Complex Software Specifications

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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This article aims at reengineering of PDF-based complex documents, where
specifications of the Object Management Group (OMG) are our initial targets.
Our motivation is that such specifications are dense and intricate to use, and
tend to have complicated structures. Our objective is therefore to create an
approach that allows us to reengineer PDF-based documents, and to illustrate
how to make more usable versions of electronic documents (such as
specifications, technical books, etc) so that end users to have a better
experience with them. The first step was to extract the logical structure of
the document in a meaningful XML format for subsequent processing. Our initial
assumption was that, many key concepts of a document are expressed in this
structure. In the next phase, we created a multilayer hypertext version of the
document to facilitate browsing and navigating. Although we initially focused
on OMG software specifications, we chose a general approach for different
phases of our work including format conversions, logical structure extraction,
text extraction, multilayer hypertext generation, and concept exploration. As a
consequence, we can process other complex documents to achieve our goals.; Comment: 27 pages, 15 figures; International Journal of Knowledge and Web
Intelligence (IJKWI)...

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## The Difference PDF of 21-cm Fluctuations: A Powerful Statistical Tool for Probing Cosmic Reionization

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 22/05/2007
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A new generation of radio telescopes are currently being built with the goal
of tracing the cosmic distribution of atomic hydrogen at redshifts 6-15 through
its 21-cm line. The observations will probe the large-scale brightness
fluctuations sourced by ionization fluctuations during cosmic reionization.
Since detailed maps will be difficult to extract due to noise and foreground
emission, efforts have focused on a statistical detection of the 21-cm
fluctuations. During cosmic reionization, these fluctuations are highly
non-Gaussian and thus more information can be extracted than just the
one-dimensional function that is usually considered, i.e., the correlation
function. We calculate a two-dimensional function that if measured
observationally would allow a more thorough investigation of the properties of
the underlying ionizing sources. This function is the probability distribution
function (PDF) of the difference in the 21-cm brightness temperature between
two points, as a function of the separation between the points. While the
standard correlation function is determined by a complicated mixture of
contributions from density and ionization fluctuations, we show that the
difference PDF holds the key to separately measuring the statistical properties
of the ionized regions.; Comment: 11 pages...

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## Predictions for high energy neutrino cross-sections from the ZEUS global PDF fits

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We have updated predictions for high energy neutrino and antineutrino charged
current cross-sections within the conventional DGLAP formalism of NLO QCD using
a modern PDF fit to HERA data, which also accounts in a systematic way for PDF
uncertainties deriving from both model uncertainties and from the experimental
uncertainties of the input data sets. Furthermore the PDFs are determined using
an improved treatment of heavy quark thresholds. A measurement of the neutrino
cross-section much below these predictions would signal the need for extension
of the conventional formalism as in BFKL resummation, or even gluon
recombination effects as in the colour glass condensate model.; Comment: 10 pages (RevTeX4), 6 figures; expanded discussion of additional
theoretical uncertainties at low x; accepted for publication in JHEP

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## The photon PDF of the proton

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/06/2014
Português

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We show how the photon input parton distribution function (PDF) may be
calculated with good accuracy, and used in an extended DGLAP global parton
analysis in which the photon is treated as an additional point-like parton. The
uncertainty of the input photon PDF is relatively small, since the major part
of the distribution (which is produced by the coherent emission of the photon
from a proton that remains intact) is well known. We present the expected
photon PDFs, and compare the predictions with ZEUS data for isolated photon
electroproduction at negative rapidities.; Comment: 11 pages, 6 figures, 3 tables

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## PDF articles metadata harvester

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/01/2013
Português

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Scientific journals are very important in recording the finding from
researchers around the world. The recent media to disseminate scientific
journals is PDF. On scheme to find the scientific journals over the internet is
via metadata. Metadata stores information about article summary. Embedding
metadata into PDF of scientific article will grant the consistency of metadata
readness. Harvesting the metadata from scientific journal is very interesting
field at the moment. This paper will discuss about scientific journal metadata
harvesters involving XMP.; Comment: 6 Pages, 9 images, 1 table

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## On the initial conditions of the 1-point PDF for incompressible Navier-Stokes fluids

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 07/03/2010
Português

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An aspect of fluid dynamics lies in the search of possible statistical models
for Navier-Stokes (NS) fluids described by classical solutions of the
incompressible Navier-Stokes equations (INSE). This refers in particular to
statistical models based on the so-called inverse kinetic theory (IKT) . This
approach allows the description of fluid systems by means a suitable 1-point
velocity probability density function (PDF) which determines, in terms of
suitable "moments", the complete set of fluid fields which define the fluid
state. A fundamental related issue lies in the problem of the unique
construction of the initial PDF. The goal of this paper is to propose a
solution holding for NS fluids. Our claim is that the initial PDF can be
uniquely determined by imposing a suitable set of physical realizability
constraints.

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## Hiding Malicious Content in PDF Documents

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 01/01/2012
Português

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This paper is a proof-of-concept demonstration for a specific digital
signatures vulnerability that shows the ineffectiveness of the WYSIWYS (What
You See Is What You Sign) concept. The algorithm is fairly simple: the attacker
generates a polymorphic file that has two different types of content (text, as
a PDF document for example, and image: TIFF - two of the most widely used file
formats). When the victim signs the dual content file, he/ she only sees a PDF
document and is unaware of the hidden content inside the file. After obtaining
the legally signed document from the victim, the attacker simply has to change
the extension to the other file format. This will not invalidate the digital
signature, as no bits were altered. The destructive potential of the attack is
considerable, as the Portable Document Format (PDF) is widely used in
e-government and in e-business contexts.; Comment: 8 pages

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## A method for reconstructing the PDF of a 3D turbulent density field from 2D observations

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 22/03/2010
Português

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We introduce a method for calculating the probability density function (PDF)
of a turbulent density field in three dimensions using only information
contained in the projected two-dimensional column density field. We test the
method by applying it to numerical simulations of hydrodynamic and
magnetohydrodynamic turbulence in molecular clouds. To a good approximation,
the PDF of log(normalised column density) is a compressed, shifted version of
the PDF of log(normalised density). The degree of compression can be determined
observationally from the column density power spectrum, under the assumption of
statistical isotropy of the turbulence.; Comment: 5 pages, 2 figures, accepted for publication in MNRAS Letters

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