Transverse Spin Physics at HERMES
  Single-spin asymmetries in semi-inclusive pion production are measured by the HERMES experiment for the first time, with a transversely polarised hydrogen target. Two different sine-dependencies are extracted which can be related to the quark distributions transversity h_1(x) and the Sivers function f_1T^perp(x). 
U. Elschenbroich, G. Schnell, R. Seidl (for the HERMES Collaboration)