Diffractive open charm production in deep-inelastic scattering and photoproduction at HERA

Measurements are presented of diffractiveopen charm production at HERA. The event topology is given by ep→eXY where the system Xcontains at least one charmed hadron and is well separated by a large rapidity gap from a leading low-mass proton remnant system Y. Two analysis techniques are used for the cross section measurements. In the first, the charm quarkis tagged by the reconstruction of a D*±(2010) meson. This technique is used in deep-inelastic scattering(DIS) and photoproduction (γp). In the second, a method based on the displacement of tracks from the primary vertex is used to measure the open charm contribution to the inclusive diffractivecross section in DIS. The measurements are compared with next-to-leading order QCD predictions based on diffractiveparton density functions previously obtained from a QCD analysis of the inclusive diffractivecross section at H1. A good agreement is observed in the full kinematic regime, which supports the validity of QCD factorization for open charm production in diffractiveDIS and γp.