Measurement of D± production in DIS with the ZEUS detector at HERA

The dominant contribution to charm production in deep inelastic scattering (DIS) at the HERA ep collider is boson-gluon fusion. Therefore the charm cross section is directly sensitive to the gluon density function in the proton as well as to the charm quark mass. A charm quark was identified by the reconstruction of the D+- meson decay D+-→K-+π+-π+-. Such weak decays allow to use the Micro-Vertex Detector (MVD) for lifetime tagging, to reduce combinatorial background and to increase the purity of the data sample. Inclusive and differential cross sections for D+- production were measured and compared with previous results. The extraction of the charm contribution to the proton structure function F2, F2c, and its inclusion into a general QCD fit allows to constrain the parton densities in the proton.