scholarly journals Polarized parton distributions in perturbative QCD

2000 ◽  
Vol 666-667 ◽  
pp. 278-281 ◽  
Author(s):  
G. Ridolfi
Keyword(s):  
Perturbative Qcd ◽  
Parton Distributions

Generalized TMDs

2015 ◽  
Vol 37 ◽  
pp. 1560037 ◽  
Author(s):  
Koichi Kanazawa ◽  
Cedric Lorcé ◽  
Andreas Metz ◽  
Barbara Pasquini ◽  
Marc Schlegel
Keyword(s):  
Angular Momentum ◽  
Transverse Momentum ◽  
Perturbative Qcd ◽  
Orbital Angular Momentum ◽  
Close Relation ◽  
Parton Distributions ◽  
Transverse Momentum Dependent ◽  
Model Independent ◽  
Mere Existence

Generalized transverse-momentum dependent parton distributions (GTMDs) encode the most general parton structure of hadrons. In this contribution, which is largely based on a recent publication,1 we focus on two twist-2 GTMDs which are denoted by F1,4 and G1,1 in parts of the literature. As already shown previously, both GTMDs have a close relation to orbital angular momentum of partons inside a hadron. However, recently even the mere existence of F1,4 and G1,1 has been doubted. We explain why this claim does not hold. We support our model-independent considerations by calculating the GTMDs in two spectator models and in perturbative QCD. For the model results we also explicitly check the relation to the orbital angular momentum of partons inside hadrons.

ASYMPTOTICS OF THE ALTARELLI-PARISI-LIPATOV EVOLUTION KERNELS OF PARTON DISTRIBUTIONS

1989 ◽  
Vol 04 (13) ◽  
pp. 1257-1276 ◽  
Author(s):  
G.P. KORCHEMSKY
Keyword(s):  
Gauge Group ◽  
Perturbative Qcd ◽  
Anomalous Dimension ◽  
Beta Function ◽  
Simple Equation ◽  
Parton Distributions ◽  
Axial Gauge ◽  
Quark Field ◽  
Cusp Anomalous Dimension

The asymptotics of the evolution kernels Pab(z) of parton distributions is investigated as z→1. It is proven that to all orders of perturbative QCD, [Formula: see text] where [Formula: see text] is the cusp anomalous dimension of the contour functionals in the fundamental (α=“quark”) and adjoint (α=“gluon”) representations of gauge group and, to the lowest orders, Cα are related to the anomalous dimension of a quark field in the axial gauge and the beta function of QCD by a simple equation.

scholarly journals PARTON DISTRIBUTIONS

2004 ◽  
Vol 19 (07) ◽  
pp. 1074-1088 ◽  
Author(s):  
R. S. THORNE
Keyword(s):  
Perturbative Qcd ◽  
Theoretical Framework ◽  
Current Understanding ◽  
Data Sets ◽  
Parton Distributions ◽  
Recent Developments ◽  
The Impact ◽  
Physical Quantities ◽  
The Way

I discuss our current understanding of parton distributions. I begin with the underlying theoretical framework, and the way in which different data sets constrain different partons, highlighting recent developments. The methods of examining the uncertainties on the distributions and those physical quantities dependent on them is analyzed. Finally I look at the evidence that additional theoretical corrections beyond NLO perturbative QCD may be necessary, what type of corrections are indicated and the impact these may have on the uncertainties.

scholarly journals QCD EVOLUTION BY FINITE ELEMENT METHODS

1994 ◽  
Vol 09 (09) ◽  
pp. 849-852 ◽  
Author(s):  
C. J. BENESH
Keyword(s):  
Finite Element ◽  
Perturbative Qcd ◽  
Finite Element Methods ◽  
Cubic Splines ◽  
New Method ◽  
Parton Distributions

A simple, new method for solving the Q2 evolution of parton distributions in perturbative QCD using cubic splines is described and applied to the evolution of non-singlet quark distributions.

scholarly journals Nuclear Parton Distributions in the DGLAP Approach

2003 ◽  
Vol 12 (02) ◽  
pp. 177-195
Author(s):  
K. J. Eskola ◽  
H. Honkanen ◽  
V. J. Kolhinen ◽  
P. V. Ruuskanen ◽  
C. A. Salgado
Keyword(s):  
Perturbative Qcd ◽  
Parton Distributions ◽  
Nucleus Scattering ◽  
Nuclear Effects

Determination of the nuclear parton distributions within the framework of perturbative QCD, the DGLAP equations in particulars, is discussed. Scale and flavour dependent nuclear effects in the parton distributions are compared with the scale and flavour independent parametrizations of HIJING and of the Hard Probe Collaboration. A comparison with the data from deep inelastic lepton-nucleus scattering and the Drell–Yan process in proton-nucleus collisions is shown.

scholarly journals Diffractive parton distributions from perturbative QCD

2005 ◽  
Vol 44 (1) ◽  
pp. 69-85 ◽  
Author(s):  
A. D. Martin ◽  
M. G. Ryskin ◽  
G. Watt
Keyword(s):  
Perturbative Qcd ◽  
Parton Distributions

PARTON DISTRIBUTION FUNCTIONS AND THE QCD-IMPROVED PARTON MODEL — AN OVERVIEW

1987 ◽  
Vol 02 (04) ◽  
pp. 1369-1387 ◽  
Author(s):  
Wu-Ki Tung
Keyword(s):  
Parton Distribution ◽  
Particle Production ◽  
Heavy Particle ◽  
Parton Model ◽  
Distribution Functions ◽  
Collider Physics ◽  
Parton Distribution Functions ◽  
Parton Distributions ◽  
First Order ◽  
Small X

Some non-trivial features of the QCD-improved parton model relevant to applications on heavy particle production and semi-hard (small-x) processes of interest to collider physics are reviewed. The underlying ideas are illustrated by a simple example. Limitations of the naive parton formula as well as first order corrections and subtractions to it are dis-cussed in a quantitative way. The behavior of parton distribution functions at small x and for heavy quarks are discussed. Recent work on possible impact of unconventional small-x behavior of the parton distributions on small-x physics at SSC and Tevatron are summarized. The Drell-Yan process is found to be particularly sensitive to the small x dependence of parton distributions. Measurements of this process at the Tevatron can provide powerful constraints on the expected rates of semi-hard processes at the SSC.

scholarly journals Double parton distributions in the pion from lattice QCD

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Gunnar S. Bali ◽  
Luca Castagnini ◽  
Markus Diehl ◽  
Jonathan R. Gaunt ◽  
Benjamin Gläßle ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Lattice Qcd ◽  
Quark Mass ◽  
Matrix Elements ◽  
Parton Distributions ◽  
Almost All ◽  
The Relationship

Abstract We perform a lattice study of double parton distributions in the pion, using the relationship between their Mellin moments and pion matrix elements of two local currents. A good statistical signal is obtained for almost all relevant Wick contractions. We investigate correlations in the spatial distribution of two partons in the pion, as well as correlations involving the parton polarisation. The patterns we observe depend significantly on the quark mass. We investigate the assumption that double parton distributions approximately factorise into a convolution of single parton distributions.

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