Time-dependent amplitude analysis of B0 --> K0S pi+ pi-

Abstract

We perform a time-dependent amplitude analysis of $B^0\to K_S^0{\pi }^{+}{\pi }^{-}$ decays to extract the CP violation parameters of $f_0(980)K_S^0$ and ${\rho }^0(770)K_S^0$ and the direct CP asymmetry of $K^{\ast +}(892){\pi }^{-}$. The results are obtained from a data sample of $(383\pm 3)\times 10^6$ $B\bar{B}$ decays, collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC. We find two solutions, with an equivalent goodness-of-fit. Including systematic and Dalitz plot model uncertainties, the combined confidence interval for values of the CP parameter ${\beta }_{eff}$ in $B^0$ decays to $f_0(980)K_S^0$ is $18^o<{\beta }_{eff}<76^o$ at 95% confidence level (C.L). CP conservation in $B^0$ decays to $f_0(980)K_S^0$ is excluded at $3.5\sigma$ including systematic uncertainties. For $B^0$ decays to ${\rho }^0(770)K_S^0$, the combined confidence interval is $-9^o<{\beta }_{eff}<57^o$ at 95% C.L. In decays to $K^{\ast +}(892){\pi }^{-}$ we measure the direct CP asymmetry to be $A_{CP}=-0.20\pm 0.10\pm 0.01\pm 0.02$. The measured phase difference (including $B^0{\bar{B}}^0$ mixing) between decay amplitudes of $B^0\to K^{\ast +}(892){\pi }^{-}$ and ${\bar{B}}^0\to K^{\ast -}(892){\pi }^{+}$, excludes the interval $-137^o<\Delta \Phi (K^{\ast +}(892){\pi }^{-})<-5^o$ at 95% C.L.

30 pages, 42 postscript figures, submitted to Phys. Rev. D