Interference fragmentation functions in electron-positron annihilation

We study the process of electron-positron annihilation into back-to-back jets, where in each jet a pair of hadrons is detected. The orientation of these two pairs with respect to each other can be used to extract the interference fragmentation functions in a clean way: for instance, from BELLE or BABAR experiment data. This is of relevance for studies of the transversity distribution function. In particular, we focus on two azimuthal asymmetries. The first one has already been studied by Artru and Collins, but is now expressed in terms of interference fragmentation functions. The second asymmetry is new and involves a function that is related to longitudinal jet handedness. This asymmetry offers a different way of studying handedness correlations