Measurements of Branching Fraction, Polarization, and Charge Asymmetry of $B^{\pm }\to {\rho }^{\pm }{\rho }^0$ and a Search for $B^{\pm }\to {\rho }^{\pm }{f}_0$(980)

We measure the branching fraction ($\mathcal{B}$), polarization ($f_L$), and $CP$ asymmetry ($A_{CP}$) of $B^{\pm }\to {\rho }^{\pm }{\rho }^0$ decays and search for the decay $B^{\pm }\to {\rho }^{\pm }{f}_0(980)$ based on a data sample of $231.8\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy $B$ factory. In $B^{\pm }\to {\rho }^{\pm }{\rho }^0$ decays we measure $\mathcal{B}=(16.8\pm 2.2\pm 2.3)\times {10}^{-6}$, $f_L=0.905\pm {0.042}_{-0.027}^{+0.023}$, and $A_{CP}=-0.12\pm 0.13\pm 0.10$, and find an upper limit on the branching fraction of $B^{\pm }\to {\rho }^{\pm }{f}_0(980)(\to {\pi }^{+}{\pi }^{-})$ decays of $1.9\times {10}^{-6}$ at 90% confidence level.

Figure 1

Projections of (a) $m_{\mathrm{ES}}$, (b) $\Delta E$, (c) $m_{{\pi }^{\pm }{\pi }^0}$, and (d) $m_{{\pi }^{+}{\pi }^{-}}$ with a cut on the ratio of the signal and background likelihoods that selects about 40% of the signal. For (a) and (b), the observable plotted is excluded from the fit in calculating the likelihood used for the enrichment selection. For (c) and (d), only the $m_{\mathrm{ES}}$, $\Delta E$, and $x_{NN}$ variables have been used in calculating the likelihood. Points represent on-resonance data, dashed lines the continuum and $B\overline{B}$ backgrounds PDFs, and solid lines the likelihood function with yields taken from the fit where all variables have been used.