Pion Oscillations

Pions produced via the $D^{+} \to \pi^{+} \overline{K^{0}}$ decay are in an entangled superposition of energy states because the $\overline{K^{0}}$ is not a mass eigenstate. This presents an opportunity to access kaon mixing parameters via $\pi$ decay accompanied by flavor tagged kaons. The pion oscillation frequency is $\Delta m_{K} \frac{m_{K}}{m_{D}}$, about 224 MHz. This method may help refine measurements of $\Delta m_{D^{0}}$ via $B^{+} \to \pi^{+} \overline{D^{0}}$.