Anomalous U(1) D-term Contribution in Type I String Models

We study the $D$-term contribution for anomalous U(1) symmetries in type I string models and derive general formula for the $D$-term contribution, assuming that the dominant source of SUSY breaking is given by $F$-terms of the dilaton, (overall) moduli or twisted moduli fields. On the basis of the formula, we also point out that there are several different features from the case in heterotic string models. The differences originate from the different forms of K"ahler potential between twisted moduli fields in type I string models and the dilaton field in heterotic string models.