scholarly journals Model independent analysis of gluonic pole matrix elements and universality of transverse-momentum-dependent fragmentation functions

2011 ◽  
Vol 83 (7) ◽  
Author(s):  
L. P. Gamberg ◽  
A. Mukherjee ◽  
P. J. Mulders
Keyword(s):  
Transverse Momentum ◽  
Matrix Elements ◽  
Transverse Momentum Dependent ◽  
Independent Analysis ◽  
Model Independent ◽  
Fragmentation Functions

BESSEL-WEIGHTED ASYMMETRIES AND TRANSVERSE SPIN EFFECTS

2012 ◽  
Vol 20 ◽  
pp. 168-176
Author(s):  
LEONARD GAMBERG
Keyword(s):  
Transverse Momentum ◽  
Cross Section ◽  
Parton Distribution ◽  
Evolution Equations ◽  
Distribution Functions ◽  
Transverse Spin ◽  
High Transverse Momentum ◽  
Transverse Momentum Dependent ◽  
Fragmentation Functions ◽  
The Cross

We consider the cross section for semi-inclusive deep inelastic scattering in Fourier space, conjugate to the outgoing hadron's transverse momentum, where convolutions of transverse momentum dependent parton distribution functions and fragmentation functions become simple products. Individual asymmetric terms in the cross section can be projected out by means of a generalized set of weights involving Bessel functions. Advantages of employing these Bessel weights are that they suppress (divergent) contributions from high transverse momentum and that soft factors cancel in (Bessel-) weighted asymmetries. Also, the resulting compact expressions immediately connect to previous work on evolution equations for transverse momentum dependent parton distribution and fragmentation functions and to quantities accessible in lattice QCD. Bessel-weighted asymmetries are thus model independent observables that augment the description and our understanding of correlations of spin and momentum in nucleon structure.

scholarly journals General helicity formalism for two-hadron production in e+e− annihilation within a TMD approach

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Umberto D’Alesio ◽  
Francesco Murgia ◽  
Marco Zaccheddu
Keyword(s):  
Transverse Momentum ◽  
Hadron Production ◽  
Probabilistic Interpretation ◽  
Leading Order ◽  
Transverse Momentum Dependent ◽  
Factorization Scheme ◽  
Helicity Formalism ◽  
Double Polarization ◽  
Fragmentation Functions ◽  
Polarization Observables

Abstract We present the complete leading-order results for the azimuthal dependences and polarization observables in e+e−→ h1h2 + X processes, where the two hadrons are produced almost back-to-back, within a transverse momentum dependent (TMD) factorization scheme. We consider spinless (or unpolarized) and spin-1/2 hadron production and give the full set of the corresponding quark and gluon TMD fragmentation functions (TMD-FFs). By adopting the helicity formalism, which allows for a more direct probabilistic interpretation, single- and double-polarization cases are discussed in detail. Simplified expressions, useful for phenomenological analyses, are obtained by assuming a factorized Gaussian-like dependence on intrinsic transverse momenta for the TMD-FFs.

NONTRIVIAL RELATIONS BETWEEN GPDs AND TMDs>

2009 ◽  
Vol 24 (35n37) ◽  
pp. 2973-2983 ◽  
Author(s):  
ANDREAS METZ ◽  
STEPHAN MEISSNER ◽  
MARC SCHLEGEL
Keyword(s):  
Transverse Momentum ◽  
Present Knowledge ◽  
The Other ◽  
Parton Distributions ◽  
Transverse Momentum Dependent ◽  
Generalized Parton Distributions ◽  
Model Independent ◽  
The One

The present knowledge about nontrivial relations between generalized parton distributions for a spin-1/2 hadron on the one hand and transverse momentum dependent distributions on the other is reviewed. While various relations can be found in the framework of simple spectator models, so far no model-independent nontrivial relations have been established. In fact, by relating the two types of parton distributions to the fully unintegrated, off-diagonal quark-quark correlator for a spin-1/2 hadron, we argue that none of the nontrivial relations can be promoted to a model-independent status.

ANALYTIC EXPRESSIONS OF CROSS SECTIONS, ASYMMETRIES AND W DENSITY MATRICES FOR e+e− → W+W− WITH GENERAL THREE-BOSON COUPLINGS

1993 ◽  
Vol 08 (19) ◽  
pp. 3285-3320 ◽  
Author(s):  
G. GOUNARIS ◽  
J. LAYSSAC ◽  
G. MOULTAKA ◽  
F. M. RENARD
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
Spin Density Matrix ◽  
Matrix Elements ◽  
Density Matrices ◽  
Independent Analysis ◽  
Analytic Expressions ◽  
Complete Set ◽  
Model Independent ◽  
High Energy Collider

We establish explicit analytic expressions for the e+e− → W+W− cross sections, asymmetries and W± spin density matrix elements in terms of the complete set of anomalous three-boson couplings. This should be useful for performing a model-independent analysis of LEP 2 or future high energy collider data. Sensitivities to the various three-boson couplings are discussed and possible ways to disentangle their effects are proposed.

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.

scholarly journals Transverse Momentum Dependent Hadron Multiplicities at COMPASS

2016 ◽  
Vol 40 ◽  
pp. 1660031
Author(s):  
Nour Makke
Keyword(s):  
Transverse Momentum ◽  
Inelastic Scattering ◽  
Deep Inelastic Scattering ◽  
Spin Structure ◽  
Parton Distributions ◽  
Transverse Momentum Dependent ◽  
Compass Experiment ◽  
Fragmentation Functions

Unpolarised semi-inclusive deep inelastic scattering is receiving a growing interest as a powerful tool to access poorly known transverse momentum dependent parton distributions and fragmentation functions that play a key role in many processes, in particular in the study of the spin structure of the nucleon. These functions can be investigated through experimental observables. New results on these observables by the COMPASS experiment at CERN will be shown and discussed.

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