Exclusive production of Ï0 mesons was studied at the COMPASS experiment by scattering 160Â GeV/c muons off transversely polarised protons. Five single-spin and three double-spin azimuthal asymmetries were measured as a function of Q2 , xBj , or pT2 . The sinÏS asymmetry is found to be â0.019Â±0.008(stat.)Â±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.

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Transverse target spin asymmetries in exclusive ρ0 muoproduction