Transverse Spin Physics at HERMES

HERMES results on azimuthal single-spin asymmetries in semi-inclusive leptoproduction of pions and charged kaons from a transversely polarised hydrogen target are presented. Preliminary results for both Collins and Sivers Fourier amplitudes are extracted with a much higher statistical significance than the evidence firstly published by HERMES for charged pions in 2005. The first evidence for a correlation between the transverse target polarization and the azimuthal orientation of the plane containing a pair of produced pions is also observed. It is expected to be related to the product of the transversity and an as-yet unmeasured dihadron fragmentation function.