Double - spin asymmetries in the cross section of ρ 0 and φ production at intermediate energies

Double-spin asymmetries in the cross section of electroproduction of ρ and φ mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive ρ electroproduction on the proton exhibits a positive tendency. This is consistent with theoretical predictions that the exchange of an object with unnatural parity contributes to exclusive ρ electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in ρ and φ meson electroproduction by quasi-real photons were also found to be consistent with zero; the asymmetry in the case of the φ meson is compatible with a theoretical prediction which involves ss̄ knockout from the nucleon.