Inclusive hadron production cross sections and angular distributions in e+ e- collisions shed light on fundamental questions of fragmentation processes. Here are presented measurements of the Collins azimuthal asymmetries in inclusive production of hadron pairs, in the e+ e- to h1 h2 X annihilation process, where the two hadrons, h1 and h2, either kaons or pions, are produced in opposite hemispheres.
The data collected by the BABAR detector allow the determination of the Collins fragmentation function dependence on hadron fractional energy for the up, down and,
for the first time, strange quarks.