Exclusive $\pi^0$ and $\eta$ Electroproduction at Multi GeV Energy and Momentum Transfer

Exclusive $\pi^0$ and $\eta$ electroproduction were measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma/dtdQ^2dx_Bd\phi$ and structure functions $\sigma_T+\epsilon\sigma_L, \sigma_{TT}$ and $\sigma_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. In addition, the ratios of $\pi^0$ to $\eta$ electroproduction were obtained. The data appear to confirm that the reactions are predominately due to transverse photons. The data are compared with Regge and handbag theoretical calculations. In the handbag framework the transverse reactions involve helicity flip of the active quarks, and transversity GPDs in which the helicity of the recoil nucleon can be either flipped or non-flipped. The data are compared with two handbag based calculations which have different combinations of GPDs.