Study of the decay B0(B0bar)-->rho+rho-, and constraints on the CKM angle alpha

Abstract

Using a data sample of 89 million Y(4s)-->B0B0bar decays collected with the BaBar detector at the PEP-II asymmetric B Factory at SLAC, we measure the B0(B0bar)-->rho+rho- branching fraction as $(30\pm 4stat\pm 5syst)\times 10^{-6}$ and a longitudinal polarization fraction of $f_L=0.99\pm 0.03sta{t}_{-0.03}^{+0.04}syst$. We measure the time-dependent-asymmetry parameters of the longitudinally polarized component of this decay as $C_L=-0.17\pm 0.27stat\pm 0.14syst$ and $S_L=-0.42\pm 0.42stat\pm 0.14syst$. We present constraints on the CKM angle $\alpha$.

Submitted to PRL