000003071 001__ 3071
000003071 005__ 20220624161120.0
000003071 037__ $$aBELLE2-CONF-PH-2022-005
000003071 041__ $$aeng
000003071 100__ $$aM.~Dorigo
000003071 245__ $$aAngular analysis of $B^+ \to \rho^+\rho^0$ decays reconstructed in 2019, 2020, and 2021 Belle~II data
000003071 260__ $$a$$c2022-06-23
000003071 300__ $$amult. p
000003071 520__ $$aWe report on a Belle II measurement of the branching fraction~($\mathcal{B}$), longitudinal polarization fraction ~($f_L$), and \CP~asymmetry~$\mathcal{A}_{\CP}$ of $B^+\to \rho^+\rho^0$ decays.  We reconstruct $B^+\to \rho^+(\to \pi^+\pi^0(\to \gamma\gamma))\rho^0(\to \pi^+\pi^-)$ decays in a sample of SuperKEKB electron-positron collisions collected by the Belle II experiment in 2019, 2020, and 2021 at the $\Upsilon$(4S) resonance and corresponding to 190\,fb$^{-1}$ of integrated luminosity.  We fit the distributions of the difference between expected and observed $B$ candidate energy, continuum-suppression variable, dipion masses, and decay angles of the resulting samples, to determine a signal yield of $345 \pm 31$ events. The signal yields are corrected for efficiencies determined from simulation and control data samples to obtain  \begin{center} $\mathcal{B}(B^+ \to \rho^+\rho^0) = [23.2^{+\ 2.2}_{-\ 2.1} (\rm stat) \pm   2.7 (\rm syst)]\times 10^{-6}$, \end{center} \begin{center} $f_{\rm L} = 0.943 ^{+\ 0.035}_{-\ 0.033} (\rm stat)\pm 0.027(\rm syst)$. \end{center} \begin{center} $\mathcal{A}_{\CP}=-0.069 \pm 0.068(\rm stat) \pm 0.060 (\rm syst)$, \end{center} The results agree  with known determinations. This is the first measurement of $\mathcal{A}_{\CP}$ in $\PBplus\to \Prhoplus\Prhozero$ decays reported by Belle II.
000003071 6531_ $$aBelle~II
000003071 6531_ $$acharmless
000003071 6531_ $$aphase 3
000003071 700__ $$aE.~Ganiev
000003071 700__ $$aR.~Manfredi
000003071 700__ $$aS.~Raiz
000003071 700__ $$aD.~Tonelli
000003071 8560_ $$friccardo.manfredi@ts.infn.it
000003071 8564_ $$uhttps://docs.belle2.org/record/3071/files/BELLE2-CONF-PH-2022-005.pdf