9 v 2 2 3 A ug 1 99 5 FERMILAB - Conf - 95 / 281 - T Potential for Discoveries in Charm Meson

The possibility of using charm meson physics to test the Standard Model (SM) is reviewed. In the case of D0 − D̄0 mixing, the SM contributions are carefully considered and the existence of a window for the observation of new physics is discussed. Some examples of extensions of the SM giving large mixing signals are presented. Finally, some distinctive aspects of CP violation and rare decays in charm mesons are discussed. The D meson has been largely overlooked as a testing ground for the SM. The reason for this might be traced back to the fact that the most important effects in Flavor Changing Neutral Currents (FCNC) and in flavor mixing are brought about, in the SM, by the top quark. This has important effects in loops that couple to external down quarks (B mixing, radiative and rare B and K decays). In the SM, top quark loops do not couple to external up quarks and thus the SM loop effects in charm physics are expected to be very small. This is the case, for instance, for D − D̄ mixing and for rare decays: the SM predicts very small rates. However this can be viewed as a window of opportunity for observing effects coming from new physics at higher energy scales. Of these, the most interesting ones are those that are relatively small or even negligible in B and K physics but become observable contributions when looking at D physics. Here we will discuss where these opportunities are likely to be and some of the new physics scenarios giving interesting signals. We will Talk delivered at the Workshop on the Tau/Charm Factory, Argonne June 21-23 1995.