Conveners
GPDs: Parallel IV
- Nicole D'Hose (CEA/IRFU,Centre d'etude de Saclay Gif-sur-Yvette (FR))
GPDs: Parallel V
- Matthias Burkardt (NMSU)
GPDs: Parallel VI
- Nicole D'Hose (CEA/IRFU,Centre d'etude de Saclay Gif-sur-Yvette (FR))
Description
3D structure of the nucleon: GPDs and Form Factors
The "flexible" parametrization of quark and gluon Generalized Parton Distributions (GPDs), based on spectator models and Regge behavior, will be presented. The Chiral Even GPDs, constrained by nucleon form factors and PDFs, determine deeply virtual Compton scattering amplitudes and are compared with cross section and polarization data. The Chiral Odd GPDs, including "transversity", contribute...
An overview of the form factor programme of the A1 Collaboration at MAMI is given. Results on the electromagnetic form factors of the proton measured with elastic electron scattering at four-momentum transfers Q2 between 0.003 and 1 GeV2/c2 are reported, which allow an extraction of the electric and magnetic radii and a determination of the two-photon exchange correction. The analysis of...
We will review the experimental program dedicated to photon electroproduction running in the Hall A of Jefferson Laboratory. First we will talk about the latest results of the E00-110 experiment running in 2004, published in Phys.Rev.C last year. Then we will present new results of photon electroproduction cross sections in the valence region (xBj=0.36) at three Q2-values (1.5, 1.75 and 2...
Investigation of GPDs and TMDs represents one of the major goals of the COMPASS-II program. Together, GPDs and TMDs provide the most complete description of the partonic structure of the nucleon. GPDs are experimentally accessible via lepton-induced exclusive reactions, in particular DVCS and DVMP. At COMPASS, these processes are investigated using a 160 GeV high intensity muon beam and a 2.5...
We show that Generalized Transverse Momentum Distributions (GTMDs) and Generalized Parton Distributions (GPDs) can be connected by Lorentz Invariant Relations (LIRs). The GTMDs have an explicit dependence on the partonic intrinsic transverse momentum and the case of unpolarized quarks in a longitudinally polarized proton is known to connect to Orbital Angular Momentum (OAM) through the GTMD...
In order to investigate the proton radius puzzle, the PRad experiment (E12-11-1062) was recently performed with 1.1 and 2.2 GeV unpolarized electron beam on a windowless H2 gas flow target in Hall B at Jefferson Lab. The experiment aims to extract the electric form factor of proton in an unprecedented low four-momentum transfer squared region, Q2 =2 × 10−4 − 0.1 (GeV/c)2, with a sub-percent...
Deeply virtual Compton scattering (DVCS) has received a lot of attention as a process to understand the transverse structure of nucleons. One feature of this cross section is the contamination from the Bethe Heitler piece, which results in cumbersome expressions. In this talk, I will discuss the helicity amplitude formalism in DVCS and its relevance in phenomenological applications.
At COMPASS DVCS and DVMP processes are studied in order to probe the partonic structure of the nucleon by constraining GPD models. Extending beyond semi-inclusive deep inelastic scattering, the measurement of lepton-induced exclusive reactions enables the study of GPDs, which ultimately reveal the three dimensional picture of the nucleon and the decomposition of its total angular momentum. The...
Although being a higher-twist contribution, the transverse response was assumed to be responsible of the large π0 electroproduction cross sections measured by the Hall A and CLAS collaboration. However no Rosenbluth separation has been performed yet to verify this assumption. We will present new results of π0 electroproduction cross sections in the valence region (xBj=0.36) at three Q2 -values...
The HERMES experiment has collected a wealth of deep inelastic scattering data using the 27.6 GeV polarized lepton beam at HERA and various pure gas targets, both unpolarized and polarized. This allowed for a series of diverse and unique measurements. Among them are measurements that provide information on the three-dimensional structure of the nucleon both in momentum space and in mixed...
