Possible Effects of Decays of Charmed-Particle Resonances

Under the assumption that production of the charmed vector meson $D^{*}$ is important in the charm threshold region, the soft cascade pion (photon) from $D^{*}\to D\pi$ ($D^{*}\to D\gamma$) for $M_{D^{*}}-M_D>M_{\pi }$ ($M_{D^{*}}-M_D<M_{\pi }$) could serve as a very useful clue for charmed particles. Also the pions produced in $e^{+}{e}^{-}$ collisions together with (strong-interaction-stable) charmed particles must obey energy equipartition. This strongly suggests other new heavy-quark thresholds and/or heavy-lepton production.