Transverse target spin asymmetries in exclusive ρ 0 muoproduction

摘要

Exclusive production ofρ0mesons was studied at the COMPASS experiment by scattering160?GeV/cmuons off transversely polarised protons. Five single-spin and three double-spin azimuthal asymmetries were measured as a function ofQ2,xBj, orpT2. Thesin?Sasymmetry is found to be?0.019±0.008(stat.)±0.003(syst.). All other asymmetries are also found to be of small magnitude and consistent with zero within experimental uncertainties. Very recent calculations using a GPD-based model agree well with the present results. The data is interpreted as evidence for the existence of chiral-odd, transverse generalized parton distributions.