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Resultados filtrados por Publicador: Universidade Cornell

## Enhanced Techniques for PDF Image Segmentation and Text Extraction

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 01/10/2012
Português

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Extracting text objects from the PDF images is a challenging problem. The
text data present in the PDF images contain certain useful information for
automatic annotation, indexing etc. However variations of the text due to
differences in text style, font, size, orientation, alignment as well as
complex structure make the problem of automatic text extraction extremely
difficult and challenging job. This paper presents two techniques under
block-based classification. After a brief introduction of the classification
methods, two methods were enhanced and results were evaluated. The performance
metrics for segmentation and time consumption are tested for both the models.; Comment: 5 pages, 5 figures

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## PDF Fits at HERA

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 09/12/2011
Português

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The HERAPDF1.0 PDF set, which was an NLO QCD analysis based on H1 and ZEUS
combined inclusive cross section data from HERA-I, has been updated to
HERAPDF1.5 by including preliminary inclusive cross section data from HERA-II
running. Studies have also been made by adding various other HERA data sets:
combined charm data, combined low energy run data and H1 and ZEUS jet data.
These data give information on the treatment of charm and the charm quark mass
and on the value of $\alpha_s(M_Z)$. The PDF analysis has also been extended to
NNLO. The PDFs give a good description of Tevatron and early LHC data.; Comment: On behalf of ZEUS and H1 collaborations, 6 pages, 6 figures. To
appear in the Proceedings of the 2011 Europhysics Conference on High Energy
Physics, HEP 2011, July 2011, Grenoble, France

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## Hessian PDF reweighting meets the Bayesian methods

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 20/08/2014
Português

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We discuss the Hessian PDF reweighting - a technique intended to estimate the
effects that new measurements have on a set of PDFs. The method stems
straightforwardly from considering new data in a usual $\chi^2$-fit and it
naturally incorporates also non-zero values for the tolerance,
$\Delta\chi^2>1$. In comparison to the contemporary Bayesian reweighting
techniques, there is no need to generate large ensembles of PDF Monte-Carlo
replicas, and the observables need to be evaluated only with the central and
the error sets of the original PDFs. In spite of the apparently rather
different methodologies, we find that the Hessian and the Bayesian techniques
are actually equivalent if the $\Delta\chi^2$ criterion is properly included to
the Bayesian likelihood function that is a simple exponential.; Comment: Transcription of the talk given in DIS2014 conference

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## Lagrangian Investigation of Auto-ignition in a Hydrogen Jet Flame in a Vitiated Co-flow: Animations of Particle Trajectories in Composition Space from PDF Model Calculations

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 07/09/2007
Português

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PDF model calculations have been performed of the Cabra lifted hydrogen flame
in a vitiated co-flow. Particle trajectories are extracted from the Lagrangian
particle method used to solve the modeled PDF equation. The particle
trajectories in the mixture fraction-temperature plane reveal (at successive
downstream locations): essentially inert mixing between the cold fuel jet and
the hot co-flow; the auto-ignition of very lean particles; and, subsequent
mixing and reaction, leading to near-equilibrium compositions. The purpose of
this paper is to present animations of the particle trajectories obtained using
different turbulent mixing models.; Comment: 5 pages, 3 figures. Video 1 (EMST)
http://ecommons.library.cornell.edu/bitstream/1813/8237/2/LIFTED_H2_EMST_FUEL.mpg
Video 2 (IEM)
http://ecommons.library.cornell.edu/bitstream/1813/8237/4/LIFTED_H2_IEM_FUEL.mpg

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## Measuring the History of Cosmic Reionization using the 21-cm Difference PDF

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 25/09/2012
Português

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During cosmic reionization, the 21-cm brightness fluctuations were highly
non-Gaussian, and complementary statistics can be extracted from the
distribution of pixel brightness temperatures that are not derivable from the
21-cm power spectrum. One such statistic is the 21-cm difference PDF, the
probability distribution function of the difference in the 21-cm brightness
temperatures between two points, as a function of the distance between the
points. Guided by 21-cm difference PDFs extracted from simulations, we perform
a maximum likelihood analysis on mock observational data, and analyze the
ability of present and future low-frequency radio array experiments to estimate
the shape of the 21-cm difference PDF, and measure the history of cosmic
reionization. We find that one-year data with an experiment such as the
Murchison Wide-field Array should suffice for probing large scales during the
mid-to-late stages of reionization, while a second-generation experiment should
yield detailed measurements over a wide range of scales during most of the
reionization era.; Comment: 11 pages, 17 figures. Submitted to MNRAS

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## Theoretical issues in PDF determination and associated uncertainties

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We study several sources of theoretical uncertainty in the determination of
parton distributions (PDFs) which may affect current PDF sets used for
precision physics at the Large Hadron Collider, and explain discrepancies
between them. We consider in particular the use of fixed-flavor versus
variable-flavor number renormalization schemes, higher twist corrections, and
nuclear corrections. We perform our study in the framework of the NNPDF2.3
global PDF determination, by quantifying in each case the impact of different
theoretical assumptions on the output PDFs. We also study in each case the
implications for benchmark cross sections at the LHC. We find that the impact
in a global fit of a fixed-flavor number scheme is substantial, the impact of
higher twists is negligible, and the impact of nuclear corrections is moderate
and circumscribed.; Comment: 18 pages, 13 figures. Final version, to be published in Phys. Lett.
B. Tab. 2 added and Fig 13 updated. Several small improvements, including
revised discussion of Ref.[24]

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## PDF uncertainties on the W boson mass measurement from the lepton transverse momentum distribution

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We study the charged current Drell-Yan process and we evaluate the proton
parton densities uncertainties on the lepton transverse momentum distribution
and their impact on the determination of the W-boson mass. We consider the
global PDF sets CT10, MSTW2008CPdeut, NNPDF2.3, NNPDF3.0, MMHT2014, and apply
the PDF4LHC recipe to combine the individual results, obtaining an uncertainty
on MW that ranges between +-18 and +-24 MeV, depending on the final state,
collider energy and kind. We discuss the dependence of the uncertainty on the
acceptance cuts and the role of the individual parton densities in the final
result. We remark that some PDF sets predict an uncertainty on MW of O(10 MeV);
this encouraging result is spoiled, in the combined analysis of the different
sets, by an important spread of the central values predicted by each group.; Comment: version accepted for publication on Phys.Rev.D, one figure and two
references added

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## Multi-variate joint PDF for non-Gaussianities: exact formulation and generic approximations

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We provide an exact expression for the multi-variate joint probability
distribution function of non-Gaussian fields primordially arising from local
transformations of a Gaussian field. This kind of non-Gaussianity is generated
in many models of inflation. We apply our expression to the non- Gaussianity
estimation from Cosmic Microwave Background maps and the halo mass function
where we obtain analytical expressions. We also provide analytic approximations
and their range of validity. For the Cosmic Microwave Background we give a fast
way to compute the PDF which is valid up to 7{\sigma} for fNL values (both true
and sampled) not ruled out by current observations, which consists of
expressing the PDF as a combination of bispectrum and trispectrum of the
temperature maps. The resulting expression is valid for any kind of
non-Gaussianity and is not limited to the local type. The above results may
serve as the basis for a fully Bayesian analysis of the non-Gaussianity
parameter.; Comment: Matches accepted verion to JCAP; conclusions unchaged, extra
references added

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## Uncertainties on alpha_S in global PDF analyses and implications for predicted hadronic cross sections

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

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We determine the uncertainty on the strong coupling alpha_S due to the
experimental errors on the data fitted in global analysis of hard-scattering
data, within the standard framework of leading-twist fixed-order collinear
factorisation in the MSbar scheme, finding that alpha_S(M_Z^2) =
0.1202^{+0.0012}_{-0.0015} at next-to-leading order (NLO) and alpha_S(M_Z^2) =
0.1171^{+0.0014}_{-0.0014} at next-to-next-to-leading order (NNLO). We do not
address in detail the issue of the additional theory uncertainty on
alpha_S(M_Z^2), but an estimate is +/-0.003 at NLO and at most +/-0.002 at
NNLO. We investigate the interplay between uncertainties on alpha_S and
uncertainties on parton distribution functions (PDFs). We show, for the first
time, how both these sources of uncertainty can be accounted for simultaneously
in calculations of cross sections, and we provide eigenvector PDF sets with
different fixed alpha_S values to allow further studies by the general user. We
illustrate the application of these PDF sets by calculating cross sections for
W, Z, Higgs boson and inclusive jet production at the Tevatron and LHC.; Comment: 45 pages, 17 figures. Grids can be found at
http://projects.hepforge.org/mstwpdf/ and in LHAPDF V5.7.1. v2: version to
appear in EPJC

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## PDF uncertainties in WH production at Tevatron

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa

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We apply a method proposed by members of CTEQ Collaboration to estimate the
uncertainty in associated $W$-Higgs boson production at Run II of the Tevatron
due to our imprecise knowledge of parton distribution functions. We find that
the PDF uncertainties for the signal and background rates are of the order 3%.
The PDF uncertainties for the important statistical quantities (significance of
the Higgs boson discovery, accuracy of the measurement of the (WH) cross
section) are smaller (1.5%) due to the strong correlation of the signal and
background.; Comment: A typo in Eq. (4) corrected

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## PDF fit in the fixed-flavor-number scheme

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 21/02/2012
Português

Relevância na Pesquisa

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We discuss the heavy-quark contribution to deep inelastic scattering in the
scheme with $n_f=3,4,5$ fixed flavors. Based on the recent ABM11 PDF analysis
of world data for deep-inelastic scattering and fixed-target data for the
Drell-Yan process with the running-mass definition for heavy quarks we show
that fixed flavor number scheme is sufficient for describing the
deep-inelastic-scattering data in the entire kinematic range. We compare with
other PDF sets and comment on the implications for measuring the strong
coupling constant $\alpha_s(M_Z)$.; Comment: 11 pages with 10 figures, to appear in the proceedings of the
"Ringberg Workshop: New Trends in HERA Physics 2011", Ringberg Castle,
Germany, 25-28 September, 2011

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