Charged-meson production and scaling violations of fragmentation functions in deeply inelastic scattering at HERA

We compare recent experimental results for one-particle-inclusive processes in deeply inelastic scattering at HERA with theoretical predictions in next-to-leading-order QCD perturbation theory, and study the factorization scale dependence of cross sections and charged multiplicities. In the future, for the HERA machine running at design luminosity, scaling violations of fragmentation functions permit the measurement of the strong coupling constant. We estimate the size of the statistical error of α_s that can be achieved, and study the theoretical error due to the various parton density parametrizations and due to the factorization scale dependence.