Search

This report reviews the recent experimental results from the CLAS collaboration (Hall B of Jefferson Lab, or JLab) on Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP) and discusses their interpretation in the framework of Generalized Parton Distributions (GPDs). The impact of the experimental data on the applicability of the GPD mechanism to these exclusive reactions is discussed. Initial results obtained from JLab 6 GeV data indicate that DVCS might already be interpretable in this framework while GPD models fail to describe the exclusive meson production (DVMP) data with the GPD parameterizations presently used. An exception is the [lowercase_phi_synonym] meson production for which the GPD mechanism appears to apply. The recent global analyses aiming to extract GPDs from fitting DVCS CLAS and world data are discussed. The GPD experimental program at CLAS12, planned with the upcoming 12 GeV upgrade of JLab, is briefly presented. [ABSTRACT FROM AUTHOR]

A physically motivated parameterization of the chiral-even generalized parton distributions (GPDs) has been obtained from a global analysis using available experimental data including nucleon electromagnetic form factors, deep inelastic scattering and DVCS. Additional information provided by lattice calculations of the higher moments of GPDs is also considered. Recently extracted observables from DVCS at JLab and Hermes are reproduced by our fit and predictions are made for higher energy regimes. Our scheme uses a Reggeized diquark model and concomitant helicity amplitude relations, which allow the extension to the chiral-odd sector. Having obtained the chiral-odd GPDs, we are able to explain the features of exclusive neutral meson electroproduction. Our analysis is applied to existing and forthcoming spin-dependent π0 and η data in the kinematical region of intermediate Bjorken x and Q2 in the multi-GeV region, accessible at present and currently planned facilities. [ABSTRACT FROM AUTHOR]

Polarization observables from vector meson photoproduction by linearly-polarized photons can be expressed in terms of bilinear combinations of helicity amplitudes parameterized by the Spin Density Matrix Elements (SDMEs). These SDMEs, which are reconstructed from the measured polarization observables, give straightforward relations for understanding the nature of the parity exchange at threshold energies, as well as for extracting signatures of the Okubo-Zweig-Iizuka violation. This paper will show our measurements of the SDMEs for reaction γp→[lowercase_phi_synonym]p from the g8b experimental dataset taken with the CLAS detector in Hall B of Jefferson Lab. In particular, we have extracted polarization observables from two separate coherent peak settings covering the respective photon energy ranges: 1.7 to 1.9 GeV (momentum transfer squared t range of -1.2 to -0.25 GeV2) and 1.9 to 2.1 GeV (t range of -1.4 to -0.25 GeV2). [ABSTRACT FROM AUTHOR]

The new experiment GlueX is currently being constructed at Jefferson Lab. The experiment was designed to search for hybrid mesons with exotic-quantum-numbers using a beam of linearly polarized photons incident on a liquid hydrogen target. We will discuss the discovery potential of the GlueX experiment and briefly overview its physics program. [ABSTRACT FROM AUTHOR]

We present the current status of a combined and simultaneous analysis of meson production reactions based on a dynamical coupled-channels (DCC) model, which is conducted at Excited Baryon Analysis Center (EBAC) of Jefferson Lab. [ABSTRACT FROM AUTHOR]

We discuss plans for Jefferson Lab to explore GPDs in hard exclusive reactions. A broad experimental program is proposed with up to 11 GeV polarized electron beams. Such an upgraded CEBAF, with high precision, and high performance detectors, will be a suitable place to study deep virtual production of mesons and photons in the range of Q[sup 2]<8 GeV/c[sup 2]. These studies are proposed as a key program for the Hall B CLAS detector. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]