Double-spin asymmetries in the cross section of and production at intermediate energiesThe HERMES Collaboration
(Received: 11 February 2003 / Published online: 11 June 2003 )
Double-spin asymmetries in the cross section of electroproduction of and mesons on the proton and deuteron are measured at the HERMES experiment. The photoabsorption asymmetry in exclusive 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 electroproduction by transverse photons. The photoabsorption asymmetry on the deuteron is found to be consistent with zero. Double-spin asymmetries in and meson electroproduction by quasi-real photons were also found to be consistent with zero; the asymmetry in the case of the meson is compatible with a theoretical prediction which involves knockout from the nucleon.
© Società Italiana di Fisica, Springer-Verlag 2003