skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Deeply Virtual Compton Scattering at JLab Hall A

Abstract

The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e,e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.

Authors:
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA
Sponsoring Org.:
USDOE - Office of Energy Research (ER)
OSTI Identifier:
917746
Report Number(s):
JLAB-PHY-07-729; DOE/OR/23177-0173; arXiv:0709.4328
TRN: US0805114
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: DIS2007, April 16-20, 2007, Munich, Germany
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ANGULAR MOMENTUM; CEBAF ACCELERATOR; COMPTON EFFECT; CROSS SECTIONS; FACTORIZATION; NEUTRONS; OPENINGS; PROTONS; QUARKS; SENSITIVITY; VALENCE

Citation Formats

Eric Voutier. Deeply Virtual Compton Scattering at JLab Hall A. United States: N. p., 2007. Web.
Eric Voutier. Deeply Virtual Compton Scattering at JLab Hall A. United States.
Eric Voutier. Mon . "Deeply Virtual Compton Scattering at JLab Hall A". United States. doi:. https://www.osti.gov/servlets/purl/917746.
@article{osti_917746,
title = {Deeply Virtual Compton Scattering at JLab Hall A},
author = {Eric Voutier},
abstractNote = {The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e,e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Apr 16 00:00:00 EDT 2007},
month = {Mon Apr 16 00:00:00 EDT 2007}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • New data points for unpolarized Deeply Virtual Compton Scattering cross sections have been extracted from the E00-110 experiment at Q 2=1.9 GeV 2 effectively doubling the statistics available in the valence region. A careful study of systematic uncertainties has been performed.
  • 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 ismore » the {phi} 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.« less
  • Generalized Parton Distributions (GPDs) are universal functions which provide a comprehensive description of hadron properties in terms of quarks and gluons. Deeply Virtual Compton Scattering (DVCS) is the simplest hard exclusive process involving GPDs. In particular, the DVCS on the neutron is mostly sensitive to E, the less constrained GPD, wich allows to access to the quark angular momentum. The first dedicated DVCS experiment on the neutron ran in the Hall A of Jefferson Lab in fall 2004. The high luminosity of the experiment and the resulting background rate recquired specific devices which are decribed in this document. The analysismore » methods and the experiment results, leading to preliminary constraints on the GPD E, are presented.« less
  • We present final results on the photon electroproduction (more » $$\vec{e}p\rightarrow ep\gamma$$) cross section in the deeply virtual Compton scattering (DVCS) regime and the valence quark region from Jefferson Lab experiment E00-110. Results from an analysis of a subset of these data were published before, but the analysis has been improved which is described here at length, together with details on the experimental setup. Furthermore, additional data have been analyzed resulting in photon electroproduction cross sections at new kinematic settings, for a total of 588 experimental bins. Results of the $Q^2$- and $$x_B$$-dependences of both the helicity-dependent and helicity-independent cross sections are discussed. The $Q^2$-dependence illustrates the dominance of the twist-2 handbag amplitude in the kinematics of the experiment, as previously noted. Thanks to the excellent accuracy of this high luminosity experiment, it becomes clear that the unpolarized cross section shows a significant deviation from the Bethe-Heitler process in our kinematics, compatible with a large contribution from the leading twist-2 DVCS$^2$ term to the photon electroproduction cross section. The necessity to include higher-twist corrections in order to fully reproduce the shape of the data is also discussed. The DVCS cross sections in this study represent the final set of experimental results from E00-110, superseding the previous publication.« less
  • Cited by 14