Target and double spin asymmetries of deeply virtual π0 production with a longitudinally polarized proton target and CLAS

摘要

The target and double spin asymmetries of the exclusive pseudoscalar channel (e) over right arrow(p) over right arrow -> ep pi(0) ere measured for the first time in the deep-inelastic regime using a longitudinally polarized 5.9 GeV electron beam and a longitudinally polarized proton target at Jefferson Lab with the CEBAF Large Acceptance Spectrometer (CLAS). The data were collected over a large kinematic phase space and divided into 110 four-dimensional bins of Q(2), x(B), -t and phi. Large values of asymmetry moments clearly indicate a substantial contribution to the polarized structure functions from transverse virtual photon amplitudes. The interpretation of experimental data in terms of generalized parton distributions (GPDs) provides the first insight on the chiral-odd GPDs (I) over tildeI(T) and E-T, and complement previous measurements of unpolarized structure functions sensitive to the GPDs H-T and (E) over bar (T). These data provide a crucial input for parametrizations of essentially unknown chiral-odd GPDs and will strongly influence existing theoretical calculations based on the handbag formalism.