We have measured the differential cross section for the [Formula presented] and [Formula presented] reactions at [Formula presented] in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at [Formula presented] exhibit a global scaling behavior for both [Formula presented] and [Formula presented] photoproduction, consistent with the constituent counting rule and the existing [Formula presented] photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive [Formula presented] to [Formula presented] photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.
|Journal||Physical Review Letters|
|State||Published - Jul 11 2003|
Bibliographical noteFunding Information:
We acknowledge the outstanding support of JLab Hall A technical staff and Accelerator Division in accomplishing this experiment. We thank R. B. Wiringa and H. Arenhövel for calculating the momentum distribution of the neutron in the deuteron. We thank Z. Chai for providing the codes to apply the R-function cut on acceptance. We also thank P. Jain and T. W. Donnelly for helpful discussions. This work was supported in part by the U.S. ?>Department of Energy, DOE/EPSCoR, the U.S. National Science Foundation, the Ministero dell’Università e della Ricerca Scientifica e Tecnologica (Murst), the French Commissariat à l’Énergie Atomique, Centre National de la Recherche Scientifique (CNRS), and the Italian Istituto Nazionale di Fisica Nucleare (INFN). This work was supported by DOE Contract No. DE-AC05-84ER40150 under which the Southeastern Universities Research Association (SURA) operates the Thomas Jefferson National Accelerator Facility.
ASJC Scopus subject areas
- Physics and Astronomy (all)