A Measurement of the Direct CP Asymmetry in the Decay $b \to s \gamma$

We present a measurement of the direct CP asymmetry in the rare Standard Model decay $b \to s \gamma$ using 380 million $B\bar{B}$ events collected by the BaBar experiment at the PEP-II $B$-factory. In the Standard Model, direct CP violation in this process is expected to be $<1$\%, while in new physics models (such as the Minimal Supersymmetric Standard Model) it can be as high as 15\%. We select this rare decay by fully reconstructing the $B$ meson decay into a fragmented $s$-quark and a photon using many exclusive final states of the $B$ decay.