On ${\varphi }_3$ Measurements Using $B^{-}\to D^{\ast }{K}^{-}$ Decays

Abstract

We point out that in decays of the type $B^{-}\to D^{\ast }{K}^{-}$, where the neutral $D^{\ast }$ meson is an admixture of $D^{\ast 0}$ and ${\bar{D}}^{\ast 0}$, there is an effective strong phase difference of $\pi$ between the cases that the $D^{\ast }$ is reconstructed as $D{\pi }^0$ and $D\gamma$. We consider the consequences for measurements of ${\varphi }_3$ using these modes, some of which are profound and beneficial.

Comments: 5 pages, no figures. To be published in Phys. Rev. D (R)