Measurement of the time-dependent CP asymmetry in B^0\to \pi^+\pi^-$ decays and observation of direct CP violation in the decay $B^0\to K^+\pi^-$

We present a measurement of the time-dependent CP asymmetry in the decay $B^0\to \pi^+\pi^-$ and observation of direct CP violation in the decay $B^0\to K^+\pi^-$, using data collected with the BaBar detector at the PEP-II asymmetric energy $e^+e^-$ collider at SLAC.