Download or read book Generalized parton distributions and nucleon structure at large x from lattice QCD written by G. Schierholz and published by . This book was released on 2004 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nucleon Structure and Generalized Parton Distributions written by Eric Voutier and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper discusses a selected part of the experimental program dedicated to the study of Generalized Parton Distributions, a recently introduced concept which provides a comprehensive framework for investigations of the partonic structure of the nucleon. Particular emphasis is put on the Deeply Virtual Compton Scattering program performed at the Jefferson Laboratory. The short and long term future of this program is also discussed in the context of the several experimental efforts aiming at a complete and exhaustive mapping of Generalized Parton Distributions.
Download or read book Nucleon Structure from Generalized Parton Distributions in Lattice QCD written by and published by . This book was released on 2005 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Generalized Parton Distributions and Nucleon Structure at Large X from Lattice QCD written by Gerrit Schierholz and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Insight Into Nucleon Structure from Generalized Parton Distributions written by R. Edwards and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The lowest three moments of generalized parton distributions are calculated in full QCD and provide new insight into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon.
Download or read book Generalized Parton Distributions and the Structure of the Nucleon written by and published by . This book was released on 2007 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Generalized Parton Distributions written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We summarize recent developments in understanding the concept of generalized parton distributions (GPDs), its relation to nucleon structure, and its application to high-Q^2 electroproduction processes. Following a brief review of QCD factorization and transverse nucleon structure, we discuss (a) new theoretical methods for the analysis of deeply-virtual Compton scattering (t-channel-based GPD parametrizations, dispersion relations); (b) the phenomenology of hard exclusive meson production (experimental tests of dominance of small-size configurations, model-independent comparative studies); (c) the role of GPDs in small-x physics and pp scattering (QCD dipole model, central exclusive diffraction). We emphasize the usefulness of the transverse spatial (or impact parameter) representation for both understanding the reaction mechanism in hard exclusive processes and visualizing the physical content of the GPDs.
Download or read book Generalized Parton Distributions and Exclusive Processes written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In last fifteen years, GPDs have emerged as a powerful tool to reveal such aspects of the QCD structure of the nucleon as: - 3D parton correlations and distributions; - spin content of the nucleon. Further advances in the field of GPDs and hard exclusive processes rely on: - developments in theory and new methods in phenomenology such as new flexible parameterizations, neural networks, global QCD fits - new high-precision data covering unexplored kinematics: JLab at 6 and 12 GeV, Hermes with recoil detector, Compass, EIC. This slide-show presents: Nucleon structure in QCD, particularly hard processes, factorization and parton distributions; and a brief overview of GPD phenomenology, including basic properties of GPDs, GPDs and QCD structure of the nucleon, and constraining GPDs from experiments.
Download or read book Generalized Parton Distributions and Their Covariant Extension written by Nabil Chouika and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generalized Parton Distributions (GPDs) encode the correlations between longitudinal momentum and transverse position of partons inside hadrons and can give access to a picture of the nucleon structure in 2+1 dimensions. They have been studied theoretically and experimentally for almost two decades and a new experimental era is starting (at JLab and COMPASS currently, and in the future at an EIC) to extract them. The difficulty is that only an indirect experimental access is so far possible, through different exclusive channels and various observables. Therefore, one has to take into account the many theoretical constraints to be able to produce accurate models and rely on their phenomenology. Two important constraints are called the polynomiality and positivity properties. The approach of this thesis is to make use of both of them by first modeling low Fock states light-front wave-functions, which gives a GPD in the DGLAP region by a parton number conserved overlap, and then covariantly extending this GPD to the ERBL region, through an inverse radon transform. In fine, the goal is to apply this on a constituent quark-like model for valence GPDs, which would allow to produce a phenomenological output (on DVCS data for instance) from this kind of models, which was impossible before. We make use of the versatile PARTONS framework to achieve this under various perturbative QCD assumptions.
Download or read book Nucleon Structure from Stochastic Estimators written by Johannes Siegfried Samir Najjar and published by Universitatsverlag Regensburg. This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of the proton and neutron, parameterized by moments of generalized parton distribution functions (GPDs), can be accessed from first principle through the computation of baryon three-point functions with lattice QCD. The numerical effort involved in such computations is quite high and thus an efficient algorithm that extracts most information at given cost is highly desirable. In this work we demonstrate that stochastic estimation techniques can efficiently increase the information/cost ratio. We examine the available results at $N_f=2$ for the nucleon axial coupling $g_A$ and iso-vector quark momentum fraction $\langle x \rangle _{u-d}$ from various collaborations and compare them to the experimental values. The tension between them is attributed to excited state contributions (ESC). We furthermore study the impact of this ESC in moments of GPDs through a model fit. This model also deals with the effects of the choice of parameters used in the computation, like the source-sink separation $t_{\mathrm{sink}}$. We demonstrate that the choice of $t_{\mathrm{sink}}$ by the Regensburg group in previous studies was reasonable and cannot account for discrepancies with the experiment. To reduce the excited state contributions in two-point functions, and consequently three-point functions, we suggest a non-Gaussian quark smearing. This is a linear combination of two Gaussian smearings with one free parameter, which can be tuned to an optimal choice with a fit.
Download or read book Structure and Spin of the Nucleon written by and published by . This book was released on 2014 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Parton distribution functions, describing longitudinal momentum, helicity and transversity distributions of quarks and gluons, have been recently generalized to account also for transverse degrees of freedom. Two new sets of more general distributions, Transverse Momentum Distributions and Generalized Parton Distributions, were introduced to describe transverse momentum and space distributions of partons. Great progress has been made since then in measurements of different Single Spin Asymmetries (SSAs) in semi-inclusive and hard exclusive processes providing access to TMDs and GPDs, respectively. Facilities world-wide involved in studies of the 3D structure of nucleon include HERMES, COMPASS, BELLE, BaBar, Halls A, B, and C at JLab, and PHENIX and STAR at RHIC (BNL). TMD studies in the Drell-Yan process are also becoming an important part of the program of hadron scattering experiments. Studies of TMDs are also among the main driving forces of the JLab 12-GeV upgrade project, several of the forward upgrade proposals of STAR and PHENIX at RHIC, and future facilities, such as the Electron Ion Collider (EIC), FAIR in Germany, and NICA in Russia. In this contribution we present an overview of the latest developments in studies of parton distributions and discuss newly released results, ongoing activities, as well as some future measurements.
Download or read book Insight Into Nucleon Structure from Lattice Calculations of Moments of Parton and Generalized Parton Distributions written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This talk presents recent calculations in full QCD of the lowest three moments of generalized parton distributions and the insight they provide into the behavior of nucleon electromagnetic form factors, the origin of the nucleon spin, and the transverse structure of the nucleon. In addition, new exploratory calculations in the chiral regime of full QCD are discussed.
Download or read book Generalized Parton Distributions in Nuclei written by Swadhin k Taneja and published by . This book was released on 2006 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Lattice QCD Results on Nucleon Structure written by Konstantinos Orginos and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: I review recent developments in lattice calculations of nucleon structure. In particular, I cover the calculations of nucleon matrix elements related to generalized parton distribution functions, structure functions and form factors.
Download or read book Spin Structure of the Nucleon written by Erhard Steffens and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive survey of the most recent results from the field of quark-gluon structure of the nucleon, in particular how the spin of the nucleon is shared by its constituents. After very intriguing results from CERN and SLAC at the end of the 1980s, the last decade has seen a set of second-generation experiments at high energy accelerators that have yielded precise information on the solution of the 'Spin Crisis' - as well as opening up new questions. The articles are written by experts from the leading collaboration and theory groups as well as providing an expert summary of the state of the art, the book points the way to future research directions. Its main focus is on semi-inclusive and exclusive measurements of deep inelastic lepton scattering, which enables for the first time the determination of the flavor-separated quark spin distributions. Future developments on generalized parton distributions and their interpretation as well as the transverse spin structure are also covered. An indispensable volume for all working in hadronic physics.
Download or read book New Model for Nucleon Generalized Parton Distributions written by and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We describe a new type of models for nucleon generalized parton distributions (GPDs) H and E. They are heavily based on the fact nucleon GPDs require to use two forms of double distribution (DD) representations. The outcome of the new treatment is that the usual DD+D-term construction should be amended by an extra term,? E+1 (x,?) which has the DD structure?/? e(?,?, with e(?,?) being the DD that generates GPD E(x,?). We found that this function, unlike the D-term, has support in the whole -1
Download or read book Generalized Parton Distributions and Angular Momentum Decomposition of the Nucleon written by Hikmat Bahadur BC and published by . This book was released on 2010 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
