scholarly journals Nucleon gluon distribution function from 2 + 1 + 1-flavor lattice QCD

2021 ◽  
pp. 2150080
Author(s):  
Zhouyou Fan ◽  
Rui Zhang ◽  
Huey-Wen Lin
Keyword(s):  
Experimental Data ◽  
Lattice Qcd ◽  
Gluon Distribution ◽  
Lattice Spacing ◽  
Distribution Functions ◽  
Coordinate Space ◽  
Lattice Calculation ◽  
Parton Distribution Functions ◽  
Independent Information ◽  
Global Fit

The parton distribution functions (PDFs) provide process-independent information about the quarks and gluons inside hadrons. Although the gluon PDF can be obtained from a global fit to experimental data, it is not constrained well in the large-[Formula: see text] region. Theoretical gluon-PDF studies are much fewer than those of the quark PDFs. In this work, we present the first lattice-QCD results that access the [Formula: see text]-dependence of the gluon unpolarized PDF of the nucleon. The lattice calculation is carried out with nucleon momenta up to 2.16 GeV, lattice spacing [Formula: see text] fm, and with valence pion masses of 310 and 690 MeV. We use reduced Ioffe-time distributions to cancel the renormalization and implement a one-loop perturbative pseudo-PDF gluon matching. We neglect mixing of the gluon operator with the quark singlet sector. Our matrix-element results in coordinate space are consistent with those obtained from the global PDF fits of CT18 NNLO and NNPDF3.1 NNLO. Our fitted gluon PDFs at both pion masses are consistent with global fits in the [Formula: see text] region.

UNCERTAINTY OF POLARIZED PARTON DISTRIBUTIONS

2003 ◽  
Vol 18 (08) ◽  
pp. 1203-1210 ◽  
Author(s):  
◽  
M. HIRAI ◽  
Y. GOTO ◽  
T. HORAGUCHI ◽  
H. KOBAYASHI ◽  
...  
Keyword(s):  
Experimental Data ◽  
Parton Distribution ◽  
Gluon Distribution ◽  
Distribution Functions ◽  
Prompt Photon ◽  
Parton Distribution Functions ◽  
Parton Distributions ◽  
Photon Process ◽  
Hessian Method ◽  
Polarized Gluon

Polarized parton distribution functions are determined by a χ2 analysis of polarized deep inelastic experimental data. In this paper, uncertainty of obtained distribution functions is investigated by a Hessian method. We find that the uncertainty of the polarized gluon distribution is fairly large. Then, we estimate the gluon uncertainty by including the fake data which are generated from prompt photon process at RHIC. We observed that the uncertainty could be reduced with these data.

scholarly journals Light-Cone Parton Distribution Functions from Lattice QCD

2018 ◽  
Vol 121 (11) ◽  
Author(s):  
Constantia Alexandrou ◽  
Krzysztof Cichy ◽  
Martha Constantinou ◽  
Karl Jansen ◽  
Aurora Scapellato ◽  
...  
Keyword(s):  
Lattice Qcd ◽  
Parton Distribution ◽  
Light Cone ◽  
Distribution Functions ◽  
Parton Distribution Functions

The contribution of valence quarks in the nucleon GE and GM

2019 ◽  
Vol 34 (27) ◽  
pp. 1950148
Author(s):  
Negin Sattary Nikkhoo ◽  
Mohammad Reza Shojaei
Keyword(s):  
Experimental Data ◽  
Angular Momentum ◽  
Form Factor ◽  
Total Angular Momentum ◽  
Form Factors ◽  
Distribution Functions ◽  
The Other ◽  
Parton Distribution Functions ◽  
Nucleon Electromagnetic Form Factor ◽  
Elastic Form

The goal of this paper is to extract the flavor decomposition of nucleon electromagnetic form factor using the modified Gaussian and extended Regge ansatzes in the GPDs. We consider the CJ15 and JR09 parton distribution functions for both of these ansatzes in calculating the nucleon elastic form factors. Our results are compared with experimental data in the range [Formula: see text] 4-momentum transfers. Also, we calculate the total angular momentum carried by quarks, the gravitational form factors, and the transverse gravitational density for quarks of the nucleon. In the end, our results are compared with the other studies.

scholarly journals Heavy light tetraquarks from Lattice QCD

2018 ◽  
Vol 175 ◽  
pp. 05014 ◽  
Author(s):  
Parikshit Junnarkar ◽  
M Padmanath ◽  
Nilmani Mathur
Keyword(s):  
Lattice Qcd ◽  
Lattice Spacing ◽  
Energy Levels ◽  
Clear Indication ◽  
Lattice Calculation ◽  
Charm Quarks ◽  
Preliminary Results ◽  
Scattering State

We present preliminary results from a lattice calculation of tetraquark states in the charm and bottom sector of the type udbb, usbb, udcc and scbb. These calculations are performed on Nf = 2 + 1 + 1 MILC ensembles with lattice spacing of a = 0:12 fm and a = 0:06 fm. A relativistic action with overlap fermions is employed for the light and charm quarks while a non-relativistic action with non-perturbatively improved coefficients is used in the bottom sector. Preliminary results provide a clear indication of presence of energy levels below the relevant thresholds of different tetraquark states in the double bottom sector while a scattering state is observed in the charm sector.

scholarly journals A Guide to Light-Cone PDFs from Lattice QCD: An Overview of Approaches, Techniques, and Results

2019 ◽  
Vol 2019 ◽  
pp. 1-68 ◽  
Author(s):  
Krzysztof Cichy ◽  
Martha Constantinou
Keyword(s):  
Lattice Qcd ◽  
Cross Sections ◽  
Light Cone ◽  
Distribution Functions ◽  
Strong Interactions ◽  
Parton Distribution Functions ◽  
Hadronic Tensor ◽  
Parton Distributions ◽  
Transverse Momentum Dependent ◽  
The Rich

Within the theory of Quantum Chromodynamics (QCD), the rich structure of hadrons can be quantitatively characterized, among others, using a basis of universal nonperturbative functions: parton distribution functions (PDFs), generalized parton distributions (GPDs), transverse momentum dependent parton distributions (TMDs), and distribution amplitudes (DAs). For more than half a century, there has been a joint experimental and theoretical effort to obtain these partonic functions. However, the complexity of the strong interactions has placed severe limitations, and first-principle information on these distributions was extracted mostly from their moments computed in Lattice QCD. Recently, breakthrough ideas changed the landscape and several approaches were proposed to access the distributions themselves on the lattice. In this paper, we review in considerable detail approaches directly related to partonic distributions. We highlight a recent idea proposed by X. Ji on extracting quasidistributions that spawned renewed interest in the whole field and sparked the largest amount of numerical studies within Lattice QCD. We discuss theoretical and practical developments, including challenges that had to be overcome, with some yet to be handled. We also review numerical results, including a discussion based on evolving understanding of the underlying concepts and the theoretical and practical progress. Particular attention is given to important aspects that validated the quasidistribution approach, such as renormalization, matching to light-cone distributions, and lattice techniques. In addition to a thorough discussion of quasidistributions, we consider other approaches: hadronic tensor, auxiliary quark methods, pseudodistributions, OPE without OPE, and good lattice cross-sections. In the last part of the paper, we provide a summary and prospects of the field, with emphasis on the necessary conditions to obtain results with controlled uncertainties.

scholarly journals QCD Factorization and PDFs from Lattice QCD Calculation

2015 ◽  
Vol 37 ◽  
pp. 1560041 ◽  
Author(s):  
Yan-Qing Ma ◽  
Jian-Wei Qiu
Keyword(s):  
Euclidean Space ◽  
Minkowski Space ◽  
Lattice Qcd ◽  
Correlation Functions ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Qcd Factorization ◽  
The Matrix

In this talk, we review a QCD factorization based approach to extract parton distribution and correlation functions from lattice QCD calculation of single hadron matrix elements of quark-gluon operators. We argue that although the lattice QCD calculations are done in the Euclidean space, the nonperturbative collinear behavior of the matrix elements are the same as that in the Minkowski space, and could be systematically factorized into parton distribution functions with infrared safe matching coefficients. The matching coefficients can be calculated perturbatively by applying the factorization formalism on to asymptotic partonic states.

scholarly journals Parton Distribution Functions and Lattice QCD

2019 ◽  
Vol 206 ◽  
pp. 01003
Author(s):  
Huey-Wen Lin
Keyword(s):  
Lattice Qcd ◽  
Parton Distribution ◽  
Pion Mass ◽  
Effective Field ◽  
Distribution Functions ◽  
Large Momentum ◽  
Parton Distribution Functions ◽  
Proton Structure ◽  
Nonperturbative Renormalization ◽  
First Time

Recently, there have been rapid developments in lattice-QCD calculations of proton structure, especially in the parton distribution functions (PDFs). We overcame a longstanding obstacle and for the first time in lattice-QCD are able to directly calculate the Bjorken-x dependence of the quark, helicity and transversity distributions. The PDFs are obtained using the large-momentum effective field theory (LaMET) framework where the full Bjorken-x dependence of finite-momentum PDFs, called “quasi-PDFs”, can be calculated on the lattice. The quasi-PDF nucleon matrix elements are renormalized non-perturbatively in RI/MOM-scheme. Following a nonperturbative renormalization of the parton quasi-distribution in a regularization-independent momentum-subtraction scheme, we establish its matching to the $ \overline {{\rm{MS}}} $ PDF and calculate the non-singlet matching coefficient at next-to-leading order in perturbation theory. In this proceeding, I will show the progress that has been made in recent years, highlighting the latest state-of-the art PDF calculations at the physical pion mass. Future impacts on the large-x global PDF fits are also discussed.

scholarly journals NUCLEAR PARTON DENSITIES AND STRUCTURE FUNCTIONS

2005 ◽  
Vol 20 (08n09) ◽  
pp. 1927-1930 ◽  
Author(s):  
S. ATASHBAR TEHRANI ◽  
ALI N. KHORRAMIAN ◽  
A. MIRJALILI
Keyword(s):  
Experimental Data ◽  
Structure Function ◽  
Nuclear Structure ◽  
Parton Distribution ◽  
Constituent Quark ◽  
Structure Functions ◽  
Constituent Quark Model ◽  
Distribution Functions ◽  
Parton Distribution Functions ◽  
Good Agreement

We calculate nuclear parton distribution functions (PDFs), using the constituent quark model. We find the bounded valon distributions in a nuclear to be related to free valon distributions in a nucleon. By using improved bounded valon distributions for a nuclear with atomic number A and the partonic structure functions inside the valon, we can calculate the nuclear structure function in x space. The results for nuclear structure-function ratio [Formula: see text] at some values of A, are in good agreement with the experimental data.

scholarly journals Pion parton distribution functions from lattice QCD

2004 ◽  
Vol 129-130 ◽  
pp. 281-283 ◽  
Author(s):  
I. Wetzorke ◽  
M. Guagnelli ◽  
K. Jansen ◽  
F. Palombi ◽  
R. Petronzio ◽  
...  
Keyword(s):  
Lattice Qcd ◽  
Parton Distribution ◽  
Distribution Functions ◽  
Parton Distribution Functions

RECENT PROGRESS ON NUCLEON STRUCTURE WITH LATTICE QCD

2014 ◽  
Vol 25 ◽  
pp. 1460039 ◽  
Author(s):  
HUEY-WEN LIN
Keyword(s):  
Lattice Qcd ◽  
Parton Distribution ◽  
Recent Progress ◽  
Distribution Functions ◽  
Nucleon Structure ◽  
Matrix Elements ◽  
Parton Distribution Functions ◽  
Bjorken X ◽  
Systematic Control ◽  
Made In

I review recent progress made in the calculation of nucleon structure in lattice QCD. Due to space limitations, I will focus on a few specific topics: systematic control of lattice-QCD matrix elements, probing TeV-physics with the aid of nucleon tensor and scalar charges, and Bjorken-x dependence of nucleon parton distribution functions.

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