Measurement of Branching Fractions for $B\to χ_{c1(2)} K (K^*)$ at Belle

Abstract

We have measured the branching fractions for the exclusive decay modes $B\to χ_{c1(2)} K(K^*)$ using a $140~{\rm fb}^{-1}$ data sample collected by the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The measured branching fractions for $B^+\to χ_{c1}K^+$, $B^0\to χ_{c1}K^0$, $B^0\to χ_{c1}K^{*0}$ and $B^+\to χ_{c1}K^{*+}$ decay modes are $(4.5\pm 0.2\pm0.5)\times 10^{-4}$, $(3.5\pm 0.3\pm0.5)\times 10^{-4}$, $(3.1\pm 0.3\pm0.7)\times 10^{-4}$ and $(4.1\pm 0.6\pm0.9)\times 10^{-4}$, respectively, where the first error is statistical and the second error is systematic. We do not observe statistically significant signals for the $B\to χ_{c2}K(K^*)$ decay modes and set upper limits at the 90% confidence level. We also study the helicity distribution for $B\to χ_{c1} K^*$ decay mode and show that the longitudinal polarization component is dominant. {{\it Keywords:} {$B$-meson, Charmonium, Branching Fractions, Polarization}} {{\it PACS:} 13.25.Hw, 11.30.Er}