Time-dependent CP violation in $B$ decays at Belle

Abstract

Using the full data sample collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider, we present three recent measurements of time-dependent CP violation in $B$ decays, and a measurement of branching fraction of the $B^0\to {\rho }^0{\rho }^0$ decay. We studied $B\to \omega K$ decays and measured the values of CP violation parameters in $B^0\to \omega K_S^0$ to be $A_{\omega K_S^0}=-0.36\pm 0.19(stat)\pm 0.05(syst)$ and $S_{\omega K_S^0}=+0.91\pm 0.32\pm 0.05$, which gives the first evidence of CP violation in this decay. In addition, we measured the direct CP violation in $B^{+}\to \omega K^{+}$ to be $A_{CP}(B^{+}\to \omega K^{+})=-0.03\pm 0.04\pm 0.01$, and two branching fractions $B(B^0\to \omega K^0)=(4.5\pm 0.4\pm 0.3)\times 10^{-6}$ and $B(B^{+}\to \omega K^{+})=(6.8\pm 0.4\pm 0.4)\times 10^{-6}$ (preliminary). From the measurement of CP violation parameters in the $B^0\to {\eta }^{\prime }{K}^0$ decay we obtain $S_{{\eta }^{\prime }{K}^0}=0.68\pm 0.07\pm 0.03$ and $A_{{\eta }^{\prime }{K}^0}=+0.03\pm 0.05\pm 0.04$ (preliminary), which are the world's most precise values to date. Measuring CP violating parameters in the $B^0\to {\pi }^{+}{\pi }^{-}$ decay gives $A_{{\pi }^{+}{\pi }^{-}}=+0.33\pm 0.06\pm 0.03$ and $S_{{\pi }^{+}{\pi }^{-}}=-0.64\pm 0.08\pm 0.03$. This result is used in an isospin analysis to constrain the ${\varphi }_2$ angle of the unitarity triangle, with which we rule out the region $23.8^{\circ }<{\varphi }_2<66.8^{\circ }$ at the $1\sigma$ confidence level. The measured branching fraction of the $B^0\to {\rho }^0{\rho }^0$ decay is $B(B^0\to {\rho }^0{\rho }^0)=(1.02\pm 0.30\pm 0.15)\times 10^{-6}$, with the fraction of longitudinally polarized ${\rho }^0$ mesons being $f_L=0.21_{-0.22}^{+0.18}\pm 0.13$. We obtain also the first evidence of the $B^0\to f_0{\rho }^0$ decay, by measuring $B(B^0\to f_0{\rho }^0)\times B(f_0\to {\pi }^{+}{\pi }^{-})=(0.86\pm 0.27\pm 0.14)\times 10^{-6}$.

for the Belle collaboration; to appear in the proceedings of EPS-HEP 2013, PoS

References in corpus (3)

• Averages of $b$-hadron, $c$-hadron, and $\tau$-lepton properties as of summer 2016
• Measurement of the CP Violation Parameters in B0 -> pi+ pi- Decays
• 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