Hard exclusive pseudoscalar meson electroproduction and spin structure of the nucleon - art. no. 014010

The amplitude for hard exclusive pseudoscalar meson electroproduction off n ucleon (nuclear) targets is computed in QCD within the leading alpha(s)lnQ( 2)/Lambda(QCD)(2) approximation. We show that the distribution of recoil nu cleons depends strongly on the angle between the momentum of the recoil nuc leon and the polarization vector of the target (or outgoing nucleon). This dependence is especially sensitive to the spin flip skewed parton distribut ion (SPD) (E) over tilde. We argue also that the scaling for this spin asym metry sets in at lower Q(2) than that for the absolute cross section. Based on the chiral quark-soliton model of the nucleon we estimate quantitativel y the spin asymmetry. In the case of pi(+) production this asymmetry is dom inated at small t by the contribution of the pion pole in the isovector SPD E as required by PCAC. In the case of KO production off a proton we find a large enhancement of the cross section as compared to the case of pi(0) pr oduction. For the forward production of neutral pseudoscalar mesons off a d euteron target we find the cross section should be zero for the zero deuter on helicity (along the gamma*D direction). We consider also cross sections of quasielastic processes off nuclei including the feasibility to implant K +,rho mesons into nuclear volume. [S0556-2821(99)05111-5].