Download or read book Relation Between Transverse Momentum Dependent Distribution Functions and Parton Distribution Functions in the Covariant Parton Model Approach written by and published by . This book was released on 2011 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: We derive relations between transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDFs f_1(x) and g_1(x) as input we predict the x- and pT-dependence of all twist-2 T-even TMDs.
Download or read book Studies on Hadron Structure Through Transverse Momentum Dependent Parton Distribution Functions written by Saman Bastami and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the main approaches toward understanding the hadronic structure is the introduction of transverse momentum dependent parton distribution functions (TMDs). These non-perturbative objects are accessible through deeply inelastic processes such as semi-inclusive deep inelastic scattering (SIDIS), Drell-Yan and e+e- annihilation. The current thesis explores the hadronic structure within the TMD approach under three independent chapters. As the first study in the present thesis the complete cross-section for the production of unpolarized hadrons in e-p semi-inclusive deep-inelastic scattering is computed up to power-suppressed O(1=Q2) terms, utilizing an approximation which systematically assumes that ̄qgq-terms are much smaller than ̄qq-correlators. All leading- and subleading-twist structure functions are calculated in terms of six TMDs and two fragmentation functions for which phenomenological extractions are available. The results are compared to available experimental data from COMPASS, HERMES and Jeerson Lab. p Drell-Yan process is the subject of the second study in this thesis. All leading-twist structure functions of -induced Drell-Yan with polarized protons are computed at the scale of COMPASS experiment. The non-perturbative inputs for the TMDs are taken from available phenomenological extractions plus two well-established models: The light-front constituent quark model and the spectator model. Evolution eects are estimated using a Gaussian ansatz with energy-dependent Gaussian widths. The results are compared to COMPASS data when available leading to important conclusions about pion and proton TMDs. Predictions are made for future experiments. The third study in this thesis aims at establishing a generalized covariant parton model that allows us to obtain all possible TMDs in a systematic way by describing the quark correlator in terms of two covariant distribution functions for on-shell partons. The proposed formulation of the model successfully reproduces all results of the original version of the model for the leading-twist time-reversal-even (T-even) TMDs and enables us to evaluate all T-even twist-3 TMDs for the first time. The unpolarized and helicity parton distribution functions are used as inputs and other TMDs are calculated then compared to available TMD parametrizations. The results show several model relations between the TMDs some of which are expected from QCD and some verified in other quark models as well.
Download or read book The Polarized TMDs in the Covariant Parton Model Approach written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We derive relations between polarized transverse momentum dependent distribution functions (TMDs) and the usual parton distribution functions (PDFs) in the 3D covariant parton model, which follow from Lorentz invariance and the assumption of a rotationally symmetric distribution of parton momenta in the nucleon rest frame. Using the known PDF $g_{1}^{q}(x)$ as input we predict the $x$- and $\mathbf{p}_{T}$-dependence of all polarized twist-2 naively time-reversal even (T-even) TMDs.
Download or read book Transverse Momentum Dependent Distribution Functions in the Bag Model written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.
Download or read book Transverse momentum dependent Parton Distributions in a Spectator Diquark Model written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Within the framework of a spectator diquark model of the nucleon, involving both scalar and axial-vector diquarks, we calculate all the leading-twist transverse-momentum-dependent parton distribution functions (TMDs). Naive Time-odd densities are generated through a one-gluon-loop rescattering mechanism, simulating the final state interactions required for these functions to exist. Analytic results are obtained for all the TMDs, and a connection with the light-cone wave functions formalism is also established. The model parameters are fixed by reproducing the phenomenological parametrizations of unpolarized and helicity parton distributions at the lowest available scale. Predictions for the other parton densities are given and, whenever possible, compared with available parametrizations.
Download or read book The Transverse Momentum Dependent Distribution Functions in the Bag Model written by and published by . This book was released on 2010 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Leading and subleading twist transverse momentum dependent parton distribution functions (TMDs) are studied in a quark model framework provided by the bag model. A complete set of relations among different TMDs is derived, and the question is discussed how model-(in)dependent such relations are. A connection of the pretzelosity distribution and quark orbital angular momentum is derived. Numerical results are presented, and applications for phenomenology discussed. In particular, it is shown that in the valence-x region the bag model supports a Gaussian Ansatz for the transverse momentum dependence of TMDs.
Download or read book Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.
Download or read book Transverse Momentum Dependent Parton Distribution Functions with Domain Wall Valence Fermions written by and published by . This book was released on 2011 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transverse Momentum Dependent Parton Distribution Functions (TMDs) reveal the intrinsic motion of quarks inside the nucleon. They are essential ingredients needed to understand angular asymmetries studied in SIDIS experiments, including current and planned experiments at JLab. Within a class B proposal, we ask for time on the Jefferson Lab computer cluster to extract amplitudes for TMDs from existing lattice QCD gauge configurations and propagators calculated by the USQCD/MILC/LHP collaborations [Aubin 2004, Bratt 2010]. The proposal encompasses more comprehensive studies with a simplified operator [Haegler 2010] along with more realistic and more demanding calculations that promise to give access to time reversal odd TMDs such as the Sivers function. We ask for cluster computer time equivalent to 1.26 million J/Psi core hours, plus disk and tape storage worth 159000 J/Psi core hours.
Download or read book Transverse Momentum Dependent TMD Parton Distribution Functions written by and published by . This book was released on 2015 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Transverse Momentum Dependent TMD Parton Distribution Functions written by R. Angeles-Martines and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Are There Approximate Relations Among Transverse Momentum Dependent Distribution Functions written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Certain {\sl exact} relations among transverse momentum dependent parton distribution functions due to QCD equations of motion turn into {\sl approximate} ones upon the neglect of pure twist-3 terms. On the basis of available data from HERMES we test the practical usefulness of one such ''Wandzura-Wilczek-type approximation'', namely of that connecting $h_{1L}^{\perp(1)a}(x)$ to $h_L^a(x)$, and discuss how it can be further tested by future CLAS and COMPASS data.
Download or read book Evolution of the Helicity and Transversity Transverse Momentum Dependent Parton Distributions written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We examine the QCD evolution of the helicity and transversity parton distribution functions when including also their dependence on transverse momentum. Using an appropriate definition of these polarized transverse momentum distributions (TMDs), we describe their dependence on the factorization scale and rapidity cutoff, which is essential for phenomenological applications.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976 with total page 680 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding the Large distance Behavior of Transverse momentum dependent Parton Densities and the Collins Soper Evolution Kernel written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: There is considerable controversy about the size and importance of non-perturbative contributions to the evolution of transverse momentum dependent (TMD) parton distribution functions. Standard fits to relatively high-energy Drell-Yan data give evolution that when taken to lower Q is too rapid to be consistent with recent data in semi-inclusive deeply inelastic scattering. Some authors provide very different forms for TMD evolution, even arguing that non-perturbative contributions at large transverse distance bT are not needed or are irrelevant. Here, we systematically analyze the issues, both perturbative and non-perturbative. We make a motivated proposal for the parameterization of the non-perturbative part of the TMD evolution kernel that could give consistency: with the variety of apparently conflicting data, with theoretical perturbative calculations where they are applicable, and with general theoretical non-perturbative constraints on correlation functions at large distances. We propose and use a scheme- and scale-independent function A(bT) that gives a tool to compare and diagnose different proposals for TMD evolution. We also advocate for phenomenological studies of A(bT) as a probe of TMD evolution. The results are important generally for applications of TMD factorization. In particular, they are important to making predictions for proposed polarized Drell- Yan experiments to measure the Sivers function.
Download or read book Transverse Momentum Dependent TMD Parton Distribution Functions written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, we review transverse momentum dependent (TMD) parton distribution functions, their application to topical issues in high-energy physics phenomenology, and their theoretical connections with QCD resummation, evolution and factorization theorems. We illustrate the use of TMDs via examples of multi-scale problems in hadronic collisions. These include transverse momentum qT spectra of Higgs and vector bosons for low qT, and azimuthal correlations in the production of multiple jets associated with heavy bosons at large jet masses. We discuss computational tools for TMDs, and present the application of a new tool, TMDLIB, to parton density fits and parameterizations.
Download or read book Generalized Parton Correlation Functions for a Spin 0 Hadron written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The fully unintegrated, off-diagonal quark-quark correlator for a spin-0 hadron is parameterized in terms of so-called generalized parton correlation functions. Such objects are of relevance for the phenomenology of certain hard exclusive reactions. In particular, they can be considered as mother distributions of generalized parton distributions on the one hand and transverse momentum dependent parton distributions on the other. Therefore, our study provides new, model-independent insights into the recently proposed nontrivial relations between generalized and transverse momentum dependent parton distributions. As a by-product we obtain the first complete classification of generalized parton distributions beyond leading twist.
Download or read book Analysis of Unintegrated Parton Distributions in Quantum Chromodynamics written by Edgar Elias and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Large Hadron Collider at CERN is currently the most powerful particle collider. It collides protons at the center of mass energy of 13 TeV. At such high energies parton densities in both protons are extremely high. This leads to the enhanced probability for multi-parton interactions. These are events in which more than one partonic interaction occurs per one nucleon collision. The multi-parton interactions, which are characterized by a hard scale, can be described in QCD by means of double parton distributions. In this thesis we propose a construction of the double unintegrated parton distribution functions which, in addition to the longitudinal momentum fractions, include the dependence on the transverse momenta of partons. To this aim, we extend the formalism that was used previously for the single unintegrated parton distribution functions. Starting from the homogeneous part of the equation for the integrated double parton distribution function, we construct the double unintegrated parton distribution functions which are the convolutions of the integrated parton densities and the Sudakov form factor. We present first numerical studies of these distributions. In particular, double unintegrated parton density functions are studied as a function of the transverse momenta for fixed scales and fixed values of the longitudinal momentum fractions. We also discuss the numerical methods used for the calculation of these double unintegrated parton distribution functions.
