Deeply Virtual Pseudoscalar Meson Production at Jefferson Lab and Transversity GPDs

Abstract

The cross section of the exclusive $π^0$ and $η$ electroproduction reaction $ep\to e^\prime p^\prime π^0/η$ was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4σ/dtdQ^2dx_Bdϕ$ and structure functions $σ_T+εσ_L, σ_{TT}$ and $σ_{LT}$ 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 $H_T^{π,η}$ and $\bar E_T^{π,η}$ were directly extracted from the experimental observables for the first time. It was found that GPD $\bar E_T$ dominates in pseudoscalar meson production. The combined $π^0$ and $η$ data opens the way for the flavor decomposition of the transversity GPDs. The first ever evaluation of this decomposition was demonstrated.