Abstract
The role of transversity or helicity-flip generalized parton distributions (GPDs) in leptoproduction of vector mesons is investigated within the framework of the handbag approach. The transversity GPDs in combination with twist-3 meson wave functions, occur in the amplitudes for transitions from a transversely polarized virtual photon to a longitudinal polarized vector meson. The importance of the transversity GPDs can be examined in some of the spin density matrix elements and in transverse target spin asymmetries. Using suitable parametrizations of both helicity-flip and non-flip GPDs, which are essentially taken from our previous papers, we estimate these observables and compare the results with available data.
Highlights
Leptoproduction of pseudoscalar mesons is an exception
The contributions from H and E are rather small in this case. Those from the transversity generalized parton distributions (GPDs) are comparably large since their contributions are enhanced by the chiral condensate which appears in the wave function for a pseudoscalar meson [9]
With regard to our results on the SDME r010 displayed in Figs. 2 and 9, and those on the interference of the γT∗ → VT amplitudes presented in [13] we find a small asymmetry AcLoLs(0φ) for ρ0 and ω production at COMPASS kinematics
Summary
Leptoproduction of pseudoscalar mesons is an exception. On the one hand, the contributions from H and E are rather small in this case. Prerequisite to such an analysis are data on, say, the π 0 cross section at reasonably large photon virtuality, Q2, and large c.m.s. energy, W Such data may come from the COMPASS experiment or the upgraded Jefferson Lab. The plan of the paper is the following: we will outline the handbag approach, referring to our previous work [9,10,13,14] and giving only details for the treatment of the contributions from the transversity GPDs. we will discuss the calculation of the subprocess amplitude for quark helicity flip and present the parametrizations of the GPDs. In Sect.
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