Observation of B± → Xc1π± and search for direct CP violation

We report the first observation of B-+/-->chi(c1)pi(+/-), a Cabibbo- and color-suppressed decay in a data sample of 386x10(6) B (B) over bar events collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We observe 55 +/- 10 signal events with a statistical significance of 6.3 sigma including systematic uncertainties. The measured branching fraction and charge-asymmetry is B(B-+/-->chi(c1)pi(+/-))=(2.2 +/- 0.4 +/- 0.3)x10(-5) and A(pi)=0.07 +/- 0.18 +/- 0.02, respectively. We also determine the ratio B(B-+/-->chi(c1)pi(+/-))/B(B-+/-->chi K-c1(+/-))=(4.3 +/- 0.8 +/- 0.3)%.