Narrow Results

The cross section of the exclusive ${\pi }^0$ and $\eta$ electroproduction reaction $ep\to e^{\prime }{p}^{\prime }{\pi }^0/\eta$ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma /dtd{Q}^{2}d{x}_{B}d{\varphi }_{\pi }$ and structure functions ${\sigma }_T+ϵ{\sigma }_L,{\sigma }_{TT}$ and ${\sigma }_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. The data are compared with the GPD based theoretical models. Analyses find that a large dominance of transverse processes is necessary to explain the experimental results. Generalized form factors of the transversity GPDs ${〈H_T〉}^{\pi ,\eta }$ and ${〈{Ē}_T〉}^{\pi ,\eta }$ were directly extracted from the experimental observables for the first time. It was found that GPD ${Ē}_T$ dominates in pseudoscalar meson production. The combined ${\pi }^0$ and $\eta$ data opens the way for the flavor decomposition of the transversity GPDs. The first ever evaluation of this decomposition was demonstrated.

A form to describe hadron strong decays is in terms of quark and gluon degrees of freedom in microscopic decay models. Initially we assume that strong decays are driven by the same inter-quark Hamiltonian which determines the spectrum, and that it incorporates gaussian confinement. An $A\to BC$ decay matrix element of the JKJ Hamiltonian involves a pair-production current matrix elements times a scattering matrix element. Diagrammatically this corresponds to an interaction between an initial line and produced pair. In this work we apply the model to the light meson sector and calculate the decay rate, comparing with the experimental values.