Experimental study of the A(e,e 'pi(+)) reaction on H-1, H-2, C-12, Al-27, Cu-63, and Au-197

Abstract

Cross sections for the H-1(e,e'pi(+))n process on H-1, H-2, C-12, Al-27, Cu-63, and Au-197 targets were measured at the Thomas Jefferson National Accelerator Facility ( Jefferson Lab) to extract nuclear transparencies. Data were taken from Q(2) = 1.1- 4.7 GeV2 for a fixed center-of-mass energy of W = 2.14 GeV. The ratio of sigma(L) and sigma(T) was extracted from the measured cross sections for H-1, H-2, C-12, and Cu-63 targets at Q(2) = 2.15 and 4.0 GeV2, allowing for additional studies of the reaction mechanism. In this article, we present the experimental setup and the analysis of the data in detail, including systematic uncertainty studies. Differential cross sections and nuclear transparencies as a function of the pion momentum at different values of Q(2) are presented. Our results are consistent with the predicted early onset of color transparency in mesons. Global features of the data are discussed and the data are compared with model calculations for the H-1(e,e'pi(+)) n reaction from nuclear targets.