Measurements of the branching fraction, polarization, and $CP$ asymmetry for the decay $B^0\to \ddot{I}‰\ddot{I}‰$

Abstract

We present a measurement of $B^0\to \ddot{I}‰\ddot{I}‰$, a charmless decay into two vector mesons, using 772 $\times 10^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. The decay is observed with a significance of 7.9 standard deviations. We measure a branching fraction $\mathcal{B}=(1.53\pm 0.29\pm 0.17)\times 10^{-6}$, a fraction of longitudinal polarization $f_L=0.87\pm 0.13\pm 0.13$, and a time-integrated $CP$ asymmetry $A_{CP}$ = $-0.44\pm 0.43\pm 0.11$, where the first uncertainties listed are statistical and the second are systematic. This is the first observation of $B^0\to \ddot{I}‰\ddot{I}‰$, and the first measurements of $f_L$ and $A_{CP}$ for this decay.

7 pages, 1 figure, submitted to Phys. Rev. Lett