Aspects of Charmonium Physics

Abstract

I review possible resolution of the $J/\psi (\psi^{\prime}) \to \rho-\pi$ puzzle based on two inputs: the relative phase between the one- photon and the gluonic decay amplitudes, and a possible hadronic excess in the inclusive nonelectromagnetic decay rate of $\psi^{\prime}$. The status of a universal large phase here is examined for its meaning and implications (including those for B-physics). Since the future of tau/charm facility(s) are again under consideration together with a future anti-proton facility at GSI, I propose to extend my review to include a broader discussion of charmonium physics. Outstanding questions like the status of the $^{1}P_{1}$ state of charmonium, measuring $D^{0}-\bar D^{0}$ mixing and relative strong phases, status of molecular P(S) - wave charmonia will also be discussed amongst others.