Neutral $D\to K{K}^{\ast }$ decays as discovery channels for charm CP violation

Abstract

We point out that the CP asymmetries in the decays $D^0\to K_S{K}^{\ast 0}$ and $D^0\to K_S\overline{K}{}^{\ast 0}$ are potential discovery channels for charm CP violation in the Standard Model. We stress that no flavor tagging is necessary, the untagged CP asymmetry $a_{CP}^{\mathrm{dir}}(D\to K_S{K}^{\ast 0})$ is essentially equal to the tagged one, so that the untagged measurement comes with a significant statistical gain. Depending on the relevant strong phase, $|a_{CP}^{\text{dir, untag}}|$ can be as large as $0.003$. The CP asymmetry is dominantly generated by exchange diagrams and does not require non-vanishing penguin amplitudes. While the CP asymmetry is smaller than in the case of $D^0\to K_S{K}_S$, the experimental analysis is more efficient due to the prompt decay $K^{\ast 0}\to K^{+}{\pi }^{-}$. One may further search for favourable strong phases in the Dalitz plot in the vicinity of the $K^{\ast 0}$ peak.

5 pages. Version to be published in Phys. Rev. Lett

References in corpus (1)

• Topological amplitudes in $D$ decays to two pseudoscalars: a global analysis with linear $SU(3{)}_F$ breaking

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