Deep Exclusive PI0 and ETA Electroproduction with CLAS at Jefferson Lab

The CLAS collaboration at Jefferson Lab has undertaken a series of measurements of exclusive $\pi^0$ and $\eta$ electroproduction at a beam energy ~ 6 GeV over a large kinematic coverage in $Q^2, t$ and $x_B$. New results of extracted structure functions $\sigma_L+\sigma_T, \sigma_{LT}$ and $\sigma_{TT}$, are presented in the kinematic range $Q^2$ from 1.2 to 3.2 GeV$^2$/c$^2$, $|t|$ from $|t_{min}|$ to 1.2 GeV$^2$/c$^2$ and $x_B$ from 0.1 to 0.6. Recent theoretical work [1,2] indicate that pseudoscalar meson production is uniquely sensitive to quark helicity-flip processes. The new results, together with CLAS measurements of beam spin asymmetries $A_\phi$ [3] and cross section ratios $\sigma(\pi_0)/\sigma(\eta)$ , compared with theoretical calculations [1,2] that are based on the helicity-flip transversity GPDs, provide supporting evidence that pseudoscalar meson production at these kinematics may be dominated by the handbag mechanism and helicity-flip transversity GPDs. \\[4pt] [1] S.V.Goloskokov and P.Kroll, Eur.Phys.J. A47,112 (2011).\\[0pt] [2] G.R. Goldstein,J.O.Gonzalez and S.Liuti, Phys. Rev., D84,034007(2011).\\[0pt] [3] R.DeMasi,et,al.(CLAS Collaboration),Phys.Rev.,C77,042201(2008)