Inclusive Charm Production in DIS

Recent measurements of inclusive $D^*$ meson production cross sections in DIS are presented in fig.23 [8,16]. The two data sets agree with each other within the large experimental errors of the preliminary H1 data and are described by the NLO QCD prediction HVQDIS [81].

Figure: a) Inclusive $D^*$ cross sections in DIS from both HERA experiments compared with a prediction from NLO QCD [8,16].

ZEUS and H1 have measured the open-charm contribution $F^{c\bar{c}}_2$ to the proton structure function $F_2$. In fig.24 the structure function $F^{c\bar{c}}_2(x,Q^2)$ is shown as a function of $x$ in different bins of $Q^2$. The data from H1 [5,43,46] and ZEUS  [15,16] are found to be in good agreement with each other and with the prediction in next-to-leading order as taken from a recent ZEUS NLO fit [68]. The data rise with increasing $Q^2$, the rise becoming steeper at lower $x$, demonstrating the property of scaling violations in charm production. The uncertainty on the theoretical prediction comes from the uncertainty of the PDF fit to the inclusive data from which the charm component is calculated dynamically, i.e.in the massive scheme. At small and moderate $Q^2$, the uncertainty in the data is comparable to the PDF uncertainty shown. This implies that the double-differential cross sections could be used as an additional constraint on the gluon density in the proton. At moderate $Q^2$ the most precise measurement of $F_2^{c\bar{c}}$ [46] is achieved by evaluation of the charm lifetime distribution in an inclusive event sample using the H1 silicon vertex detector. Details of the analysis method and results are given in sections 5.5.2 and  6.2.2.

Figure: Measurements of the contribution $F_2^{c\bar{c}}$ from charm to the proton structure function $F_2(x,Q^2)$. The H1 and ZEUS data are presented as functions of $x$ in different bins of $Q^2$ and compared with a prediction at next-to-leading order.