Measurement of Collins Asymmetries in the inclusive production of hadron pairs

Transversity distribution, which describes the quark transverse polarisation inside a transversely polarised nucleon, is the last leading-twist missing piece of the QCD description of the partonic structure of the nucleon. Transversity can be extracted from semi-inclusive deep inelastic scattering data, where, however, it couples to a new, unknown fragmentation function, called Collins function. We present a measurement of the azimuthal asymmetries in the process $e^+e^- \to \pi \pi X$ (inclusive hadron production), in which the two pions are produced in opposite hemispheres, based on the full {\sl B{\scriptsize A}B{\scriptsize AR}} data sample. The Collins function is extracted from the measured asymmetries.