Additional spin-0 particles appear in many extensions of the standard model. We search for long-lived spin-0 particles S in B-meson decays mediated by a b→s quark transition in e+e− collisions at the Υ(4S) resonance at the Belle II experiment. Based on a sample corresponding to an integrated luminosity of 189 fb−1, we observe no evidence for signal. We set model-independent upper limits on the product of branching fractions B(B0→K∗(892)0(→K+π−)S)×B(S→x+x−) and B(B+→K+S)×B(S→x+x−), where x+x− indicates e+e−,μ+μ−,π+π−, or K+K−, as functions of S mass and lifetime at the level of 10−7.
