Direct probes of flavor-changing neutral currents in e+e−-collisions

We propose a novel method to study flavor-changing neutral currents in the e+e− → D∗0 and e+e− → Bs∗ transitions, tuning the energy of e+e−- collisions to the mass of the narrow vector resonance D∗0 or Bs∗. We present a thorough study of both short-distance and long-distance contributions to e+e− → D∗0 in the Standard Model and investigate possible contributions of new physics in the charm sector. This process, albeit very rare, has clear advantages with respect to the D0 → e+e− decay: the helicity suppression is absent, and a richer set of effective operators can be probed. Implications of the same proposal for Bs∗ are also discussed.