Exclusive ρ0 muoproduction on transversely polarised protons and deuterons

The transverse target spin azimuthal asymmetry View the MathML source in hard exclusive production of ρ0 mesons was measured at COMPASS by scattering 160 GeV/c muons off transversely polarised protons and deuterons. The measured asymmetry is sensitive to the nucleon helicity-flip generalised parton distributions Eq, which are related to the orbital angular momentum of quarks in the nucleon. The Q2, xBj and View the MathML source dependence of View the MathML source is presented in a wide kinematic range: View the MathML source, 0.003<xBj<0.3 and View the MathML source for protons or View the MathML source for deuterons. Results for deuterons are obtained for the first time. The measured asymmetry is small in the whole kinematic range for both protons and deuterons, which is consistent with the theoretical interpretation that contributions from GPDs Eu and Ed approximately cancel.