It is reported on an analysis of electroproduction of light vector mesons at small Bjorken-x (xBj) within the handbag approach. The partonic subprocesses, meson electroproduction off quarks or gluons, are calculated within the modified perturbative approach (m.p.a.) in which quark transverse momenta are retained. The soft hadronic matrix elements, generalized parton distributions (GPDs), are co...

We consider a sub-leading twist chiral-odd pion fragmentation function and explore its contribution in single pion semi-inclusive electroproduction. We evaluate the single beam-spin azimuthal asymmetry ALU and the double spin asymmetry ALT in polarized electroproduction of pions from an unpolarized and transversely polarized nucleon respectively. The beam asymmetry is expressed as the product o...

Exclusive coherent and incoherent electroproduction of the p° meson from H and N targets has been studied at the HERMES experiment as a function of coherence length (lc), corresponding to the lifetime of hadronic fluctuations of the virtual photon, and squared fourmomentum of the virtual photon (—<2). The ratio of N to *H cross sections per nucleon, called nuclear transparency, was found to inc...

Generalized nucleon polarizabilities for virtual photons can be deened in terms of electroproduction cross sections as function of the 4-momentum transfer Q 2. In particular, the sum of the generalized electric and magnetic polarizabilities = + and the spin polarizability can be expressed by virtual photon absorption cross sections integrated over the excitation energy. These quantities have be...

This manual describes the formalism and use of the program EPIPROD to compute observables and response functions for the electroproduction of pseu-doscalar mesons upon nucleons.