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

Abstract

Double-spin asymmetries in the cross section of electroproduction of $ρ^0$ and $ϕ$ mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive $ρ^0$ 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 $ρ^0$ electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in $ρ^0$ 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 $s\bar{s}$ knockout from the nucleon.