Rare Charm Decays

Rare FCNC decay modes of charmed mesons are reviewed. The standard model predictions, including both short and long distance contributions, are summarized. Several new physics options that can give detectable signals are described.Comment: 4 pages. Presented at the 6th International Conference on Hyperons, Charm and Beauty Hadrons, IIT, Chicago, june 27-july 3, 2004. To be published in the Proceeding

A Possible Arena for Searching New Physics - the Γ(D0→ρ0γ)/Γ(D0→ωγ)\Gamma(D^0 \to \rho^0 \gamma)/\Gamma (D^0 \to \omega \gamma) Ratio

We propose to investigate flavour changing neutral currents in the $c \to u \gamma$ transition through the measurement of the difference between $\Gamma (D^0 \to \rho^0 \gamma)$ and $\Gamma (D^0 \to \omega \gamma)$. This is based on the observation that $D^0 \to (d \bar d) \gamma$ is due to long distance physics while $D^0 \to (u \bar u) \gamma$ arises from the $c \to u \gamma$ transition. The effect of $\rho - \omega$ mixing is included. A difference in the decay widths of more than about 30% would be indicative of new physics.Comment: 7 pages, 1 figure include