Measurement of the branching fraction, polarization, and time-dependent $CP$ asymmetry in $B^0\to {\rho }^{+}{\rho }^{-}$ decays and constraint on the CKM angle ${\varphi }_2$

Abstract

We present a measurement of the branching fraction and fraction of longitudinal polarization of $B^0\to {\rho }^{+}{\rho }^{-}$ decays, which have two ${\pi }^0$'s in the final state. We also measure time-dependent {\it CP} violation parameters for decays into longitudinally polarized ${\rho }^{+}{\rho }^{-}$ pairs. This analysis is based on a data sample containing $(387\pm 6)\times 10^6$ ${\rm Y}(4S)$ mesons collected with the Belle~II detector at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider in 2019-2022. We obtain $\mathcal{B}(B^0\to {\rho }^{+}{\rho }^{-})=(2.89_{-0.22}^{+0.23}{}_{-0.27}^{+0.29})\times 10^{-5},f_L=0.921_{-0.025}^{+0.024}{}_{-0.015}^{+0.017}$, \mbox{$S=-0.26\pm 0.19\pm 0.08$}, and $C=-0.02\pm 0.12_{-0.05}^{+0.06}$, where the first uncertainties are statistical and the second are systematic. We use these results to perform an isospin analysis to constrain the CKM angle ${\varphi }_2$ and obtain two solutions; the result consistent with other Standard Model constraints is ${\varphi }_2=(92.6_{-4.7}^{+4.5}{)}^{\circ }$.

References in corpus (30)

• An Introduction to PYTHIA 8.2
• CP Violation and the CKM Matrix: Assessing the Impact of the Asymmetric B Factories
• The Precision Monte Carlo Event Generator KK For Two-Fermion Final States In e+e- Collisions
• sPlot: a statistical tool to unfold data distributions
• Model-independent constraints on Delta F=2 operators and the scale of New Physics
• SuperKEKB Collider
• Current status of the Standard Model CKM fit and constraints on $\Delta F=2$ New Physics
• The Belle II Core Software
• Evidence for B0->pi0pi0
• Towards the Identification of New Physics through Quark Flavour Violating Processes
• Impact of tag-side interference on time-dependent CP asymmetry measurements using coherent B0 B0bar pairs
• Observation of B+ -> rho+ rho0
• Low Energy Probes of PeV Scale Sfermions
• First Measurements of Beam Backgrounds at SuperKEKB
• A Study of B0 to rho+rho- Decays and Constraints on the CKM Angle alpha
• New physics in $B$ meson mixing: future sensitivity and limitations
• The Design, Construction, Operation and Performance of the Belle II Silicon Vertex Detector
• Global Decay Chain Vertex Fitting at B-Factories
• Front-end electronic readout system for the Belle II imaging Time-Of-Propagation detector
• Isospin analysis of charmless B-meson decays
• Observation of the $B^0\to {\rho }^0{\rho }^0$ decay from an amplitude analysis of $B^0\to ({\pi }^{+}{\pi }^{-})({\pi }^{+}{\pi }^{-})$ decays
• Measurement of the integrated luminosity of data samples collected during 2019-2022 by the Belle II experiment
• Measurements of branching fraction, polarization, and charge asymmetry of B+ --> rho+ rho0 and a search for B+ --> rho+ f0(980)
• Measurements of Beam Backgrounds in SuperKEKB Phase 2
• Study of B^0 -> rho^0 rho^0 decays, implications for the CKM angle phi_2 and search for other B^0 decay modes with a four-pion final state
• Study of ${\mathbf{B}}^0\to {\rho }^{+}{\rho }^{-}$ decays and implications for the CKM angle ${\varphi }_2$
• New graph-neural-network flavor tagger for Belle II and measurement of $\sin 2{\varphi }_1$ in $B^0\to J/\psi K_{\text{S}}^0$ decays
• Measurement of the $B^0$ lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data
• Measurement of decay-time-dependent $\text{CP}$ violation in $B^0\to J/\psi K_S^0$ decays using 2019-2021 Belle II data
• Probing the high scale SUSY in CP violations of K, B0 and Bs mesons