Measurement of $\gamma$ in $B^\pm \to D^{(*)0} K^\pm$ decays by a Dalitz analysis of $D^0 \to K_S \pi^- \pi^+$

We present the measurement of the unitary triangle angle $\gamma$ obtained studying the direct CP violation in the decay $B^\pm \to D^{(*)0} K^\pm$ (with $D^* \to D^0 \pi^0,D^0 \gamma$) and $D^0 \to K_S \pi^- \pi^+$. The method is based on the analysis of Dalitz distribution of the three-body decay of the neutral D meson and exploits the interference between $D^0$ and $\bar{D}^0$ to extract both the weak and strong phases. The analysis is performed using a sample of 227 million $B \bar{B}$ pairs recorded at the $\Upsilon(4S)$ resonance with the $BaBar$ detector at the $PEP-II$ asymmetric $e^+e^-$ storage rings.