# Improved Measurement of $B^+\to\rho^+\rho^0$ and Determination of the Quark-Mixing Phase Angle $\alpha$

Abstract : We present improved measurements of the branching fraction ${\cal B}$, the longitudinal polarization fraction $f_L$, and the direct {\ensuremath{CP}\xspace} asymmetry {\ensuremath{{\cal A}_{CP}}\xspace} in the $B$ meson decay channel $B^+\to\rho^+\rho^0$. The data sample was collected with the {{\slshape B\kern-0.1em{\smaller A}\kern-0.1em B\kern-0.1em{\smaller A\kern-0.2em R}}} detector at SLAC. The results are ${\cal B} (\Bp\ra\rprz)=(23.7\pm1.4\pm1.4)\times10^{-6}$, $f_L=0.950\pm0.015\pm0.006$, and $\Acp=-0.054\pm0.055\pm0.010$, where the uncertainties are statistical and systematic, respectively. Based on these results, we perform an isospin analysis and determine the CKM weak phase angle $\alpha$ to be $(92.4^{+6.0}_{-6.5})^{\circ}$.
Document type :
Journal articles

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Submitted on : Friday, January 23, 2009 - 12:57:04 PM
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### Citation

B. Aubert, y. Karyotakis, J. P. Lees, V. Poireau, E. Prencipe, et al.. Improved Measurement of $B^+\to\rho^+\rho^0$ and Determination of the Quark-Mixing Phase Angle $\alpha$. Physical Review Letters, American Physical Society, 2009, 102, pp.141802. ⟨10.1103/PhysRevLett.102.141802⟩. ⟨in2p3-00355607⟩

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