Study of CP-violating asymmetries in B^0 --> pi^+pi^-, K^+pi^- decays

Abstract

We present a measurement of the time-dependent CP-violating asymmetries in neutral B decays to the ${\pi }^{+}{\pi }^{-}$ CP eigenstate, and an updated measurement of the charge asymmetry in $B^0\to K^{+}{\pi }^{-}$ decays. In a sample of 33 million ${\rm Y}(4S)\to B\bar{B}$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric $B$ Factory, we find $65_{-11}^{+12}$ ${\pi }^{+}{\pi }^{-}$ and $217\pm 18$ $K^{+}{\pi }^{-}$ candidates and measure the asymmetry parameters $S_{\pi \pi }=0.03_{-0.56}^{+0.53}\pm 0.11$, $C_{\pi \pi }=-0.25_{-0.47}^{+0.45}\pm 0.14$, and ${\mathcal{A}}_{K\pi }=-0.07\pm 0.08\pm 0.02$, where the first error is statistical and the second is systematic.

8 pages, 2 figrues, submitted to Physical Review D (rapid communications)