Cross-Section Measurement of Charged-Pion Photoproduction from Hydrogen and Deuterium

We have measured the differential cross section for the b3;n࢐c0;^-p and b3;n࢐c0;⁺ reactions at c.m. = 90° in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E3.3 GeV exhibit a global scaling behavior for both c0;^- and c0;⁺ photoproduction, consistent with the constituent counting rule and the existing c0;⁺ 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 c0;^- to c0;⁺ photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.