We present measurements of CP-violating parameters in B-0 ((B) over bar (0)) --> eta'K-S(0) and B+/- --> eta'K+/- decays based on a 41.8 fb(-1) data sample collected at the gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We fully reconstruct one neutral B meson as a B-0((B) over bar (0)) --> eta'K-S(0) CP eigenstate and identify the flavor of the accompanying B from its decay products. From the distribution of proper time intervals between pairs of B meson decay points, we obtain the CP-violating asymmetry parameters S-eta'KS(0) = 0.28+/-0.55(stat)(-0.08)(+0.07)(syst), and A(eta'KS)(0) = 0.13+/-0.32(stat)(-0.06)(+0.09)(syst). We also reconstruct charged B+/- --> eta'K+/- decays and determine a direct- CP-violating asymmetry value of A(eta'K)(+/-) = (-1.5+/-7.0(stat) +/- 0.9(syst))%.(C) 2002 Elsevier Science B.V. All rights reserved.
