Model and form factor dependence in the reactionep→e'K+Λ

Abstract

The reaction $\mathit{ep}\ensuremath{\rightarrow}{e}^{'}{K}^{+}\ensuremath{\Lambda}$ was investigated using a tree-level effective Lagrangian model with coupling parameters fit to empirical cross sections for the reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}\ensuremath{\Lambda}$. The model incorporates both spin $\frac{1}{2}$ and spin $\frac{3}{2}$ resonances in the $s$ and $u$ channels, as well as $K(892)$ and $K(1270)$ resonances in the $t$ channel. Results for the electroproduction cross sections were obtained with four different photoproduction fits, which yield roughly equivalent descriptions of the empirical photoproduction cross sections but which vary in their predictions for photoproduction polarization observables. Electromagnetic form factors are incorporated in a manner similar to previous calculations except that a multiplicative factor is introduced into the masses associated with the $s$- and $u$-channel transition form factors so that the sensitivity of the calculated cross sections to these form factors can be studied. Results are presented for the unpolarized differential cross section in a variety of kinematical situations and for particular contributions to the cross section in one particular kinematic situation. The sensitivity of the results to both the photoproduction fit employed and to the transition form factors depends to some extent on the kinematics, but in general, the calculated cross sections are more sensitive to the transition form factors than to the photoproduction fit. Our results suggest that electroproduction data, in conjunction with a reaction model that quantitatively fits the photoproduction data, may provide significant constraints on the electromagnetic form factors associated with resonance excitation.