Observation of B^{\pm} \to χ_{c1} π^{\pm} and Search for Direct CP Violation

Abstract

We report the first observation of $B^{\pm }\to {\chi }_{c1}{\pi }^{\pm }$, the Cabibbo- and color-suppressed decay in a data sample of $386\times 10^6$~$B\bar{B}$ events collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We observe $55\pm 10$ signal events with a statistical significance of $6.3\sigma$ including systematic uncertainties. The measured branching fraction and charge-asymmetry is $\mathcal{B}(B^{\pm }\to {\chi }_{c1}{\pi }^{\pm })=(2.2\pm 0.4\pm 0.3)\times 10^{-5}$ and ${\mathcal{A}}_{\pi }=0.07\pm 0.18\pm 0.02$, respectively. We also determine the ratio $\mathcal{B}(B^{\pm }\to {\chi }_{c1}{\pi }^{\pm })/\mathcal{B}(B^{\pm }\to {\chi }_{c1}{K}^{\pm })=(4.3\pm 0.8\pm 0.3)$.

5 Pages, 4 figures, BELLE-CONF-0644 (ICHEP06), Submitted to PRD(RC)

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