DirectCPViolation inB→ϕKsand New Physics

In the presence of large new physics contributions to loop-induced $b\to s$ transitions, sizable direct $CP$ violation in $B\to \varphi K$ decays is expected on general grounds. We compute explicitly $CP$-violating effects using QCD factorization and find that, even in the restricted case in which new physics has the same penguin structure as the standard model, the rate asymmetry can be of the order of 1. We briefly discuss a more general scenario and comment on the inclusion of power-suppressed corrections to factorization.