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Jimenez-Delgado, Pedro

Publications and source records attributed to Jimenez-Delgado, Pedro.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Reply to comment on ''New limits on intrinsic charm in the nucleon from global analysis of parton distribution''

We reply to the Comment of Brodsky and Gardner on our paper "New limits on intrinsic charm in the nucleon from global analysis of parton distributions" [Phys. Rev. Lett. 114, 082002 (2015)]. We address a number of incorrect claims made about our fitting methodology, and elaborate how global QCD analysis of all available high-energy data provides no evidence for a large intrinsic charm component of the nucleon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

New Limits on Intrinsic Charm from a QCD Global Analysis

We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by recent model calculations on the light-front. The analysis makes use of the full range of available high-energy scattering data for Q2?1~GeV2 and W2?3.5~GeV2, including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with ?x?IC at most 0.5\% (corresponding to an IC normalization of ?1%) at the 4? level for ??2=1. We also critically assess the impact of older EMC measurements of Fc2 at large x, which favor a nonzero IC, but with very large ?2 values.

Hobbs, Timothy↗
DOE OSTI2015

New Limits on Intrinsic Charm in the Nucleon from Global Analysis

We present a new global QCD analysis of parton distribution functions, allowing for possible intrinsic charm (IC) contributions in the nucleon inspired by light-front models. The analysis makes use of the full range of available high-energy scattering data for Q2>1 GeV2 and W2>3.5 GeV2, including fixed-target proton and deuteron cross sections at lower energies that were excluded in previous global analyses. The expanded data set places more stringent constraints on the momentum carried by IC, with ?x?IC at most 0.5% (corresponding to an IC normalization of ?1%) at the 4? level for ??2=1. We also critically assess the impact of older EMC measurements of Fc2 at large x, which favor a nonzero IC, but with very large ?2 values.

Melnitchouk, Wolodymyr↗
DOE OSTI2015

Delineating the polarized and unpolarized partonic structure of the nucleon

Reports on our latest extractions of parton distribution functions of the nucleon are given. First an overview of the recent JR14 upgrade of our unpolarized PDFs, including NNLO determinations of the strong coupling constant and a discussion of the role of the input scale in parton distribution analysis. In the second part of the talk recent results on the determination of spin-dependent PDFs from the JAM collaboration are reported, including a careful treatment of hadronic and nuclear corrections, as well as reports on the impact of present and future data in our understanding of the spin of the nucleon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Impact of hadronic and nuclear corrections on global analysis of spin-dependent parton distributions

We present the first results of a new global next-to-leading order analysis of spin-dependent parton distribution functions from the most recent world data on inclusive polarized deep-inelastic scattering, focusing in particular on the large-x and low-Q^2 regions. By directly fitting polarization asymmetries we eliminate biases introduced by using polarized structure function data extracted under nonuniform assumptions for the unpolarized structure functions. For analysis of the large-x data we implement nuclear smearing corrections for deuterium and 3He nuclei, and systematically include target mass and higher twist corrections to the g_1 and g_2 structure functions at low Q^2. We also explore the effects of Q^2 and W^2 cuts in the data sets, and the potential impact of future data on the behavior of the spin-dependent parton distributions at large x.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Extractions of polarized and unpolarized parton distribution functions

An overview of our ongoing extractions of parton distribution functions of the nucleon is given. First JAM results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering are presented first, and followed by a short report on the status of the JR unpolarized parton distributions. Different aspects of PDF analysis are briefly discussed, including effects of the nuclear structure of targets, target-mass corrections and higher twist contributions to the structure functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

First JAM results on the determination of polarized parton distributions

The Jefferson Lab Angular Momentum (JAM) Collaboration is a new initiative to study the angular momentum dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions at intermediate and large x from world data on polarized deep-inelastic scattering are presented. Different aspects of global QCD analysis are discussed, including the effects of nuclear structure of deuterium and {sup 3}He targets, target mass corrections and higher twist contributions to the g{sub 1} and g{sub 2} structure functions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

First JAM results on the determination of polarized parton distributions

The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed at the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering will be presented and compared with previous determinations from other groups. Different aspects of global QCD analysis will be discussed, including effects due to the nuclear structure of deuteron and Helium targets, target-mass corrections and higher twist contributions to the g1 structure function as well as the g2 structure function.

Jimenez-Delgado, Pedro↗
DOE OSTI2013

Comparative study of nonperturbative heavy quarks in the nucleon

We perform an analysis of the role of nonperturbative (or intrinsic) charm in the nucleon. Charm is generated nonperturbatively through Fock state expansions of the nucleon wave function to include five-quark virtual states involving charmed mesons and baryons. We consider contributions from a variety of charmed meson-baryon states and find surprisingly dominant effects from the D¯?0?+c configuration. Particular attention is paid to the existence and persistence of high-x structure for intrinsic charm, and the x dependence of the c?c¯ asymmetry predicted in meson-baryon models. We also discuss efforts to constrain intrinsic charm via a forthcoming global QCD analysis, and the possibility of extracting intrinsic strangeness using a similar approach.

Hobbs, Timothy↗
DOE OSTI2013

Parton Momentum and Helicity Distributions in the Nucleon

We review the current status of spin-averaged and spin-dependent parton distributions functions (PDFs) of the nucleon. After presenting the formalism used to fit PDFs in modern global data analyses, we discuss constraints placed on the PDFs by specific data types. We give representative examples of unpolarized and polarized PDFs and their errors, and list open questions in global QCD fitting. Finally, we anticipate how future facilities, with fixed-target and collider experiments, may impact our knowledge of PDFs and reduce their uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Delineating gluon PDFs and the strong coupling

Overview of the ongoing update of the JR unpolarized parton distribution functions with particular focus on our interim results for the gluon distributions and the strong coupling constant.

Jimenez-Delgado, Pedro↗
DOE OSTI2013

First JAM results on the determination of polarized parton distributions

The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed to the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering will be presented and compared with previous determinations from other groups. Different aspects of global QCD analysis will be discussed, including effects due to nuclear structure, higher twist, and target-mass corrections, as well as the impact of different data selections.

Jimenez-Delgado, Pedro↗
DOE OSTI2013

First JAM results on the determination of polarized parton distributions

The Jefferson Lab Angular Momentum (JAM) collaboration is a new initiative aimed to the study of the angular-momentum-dependent structure of the nucleon. First results on the determination of spin-dependent parton distribution functions from world data on polarized deep-inelastic scattering will be presented and compared with previous determinations from other groups. Different aspects of global QCD analysis will be discussed, including effects due to nuclear structure, higher twist, and target-mass corrections, as well as the impact of different data selections.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

The role of the input scale in parton distribution analyses

A first systematic study of the effects of the choice of the input scale in global determinations of parton distributions and QCD parameters is presented. It is shown that, although in principle the results should not depend on these choices, in practice a relevant dependence develops as a consequence of what is called procedural bias. This uncertainty should be considered in addition to other theoretical and experimental errors, and a practical procedure for its estimation is proposed. Possible sources of mistakes in the determination of QCD parameter from parton distribution analysis are pointed out.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗