Nonsinglet kaon fragmentation function from e⁺e^- kaon production

We perform fits to the available charged and neutral kaon-production data in e⁺+e^-→K+X, K=K^±, and KS0, and determine the nonsinglet combination of kaon fragmentation functions DuK ^±-DdK^± in a model independent way and without any correlations to the other fragmentation functions. Only nuclear isospin invariance is assumed. Working with nonsinglets allows us to include the data at very low momentum fractions, which have so far been excluded in global fits, and to perform a first next-next-to leading order fit to fragmentation functions. We find that the kaon nonsinglet fragmentation function at large z is larger than that obtained by the other collaborations from global fit analysis and differs significantly at low z.