Effect of fourth generation CP phase on b → s transitions

We study the effect of a sequential fourth generation on b --> sgamma, B-s mixing, B --> K((*))l(+)l(-), X(s)l(+)l(-) and phiK(S), taking into account the presence of a new CP phase in quark mixing. We find that the effects via electromagnetic and strong penguins, such as in b --> sgamma or CP-violation in B --> phiK(S), are rather mild, but the impact via boxes or Z penguins is quite significant. Not only can one have a B-s mixing much larger than expected, even if it is measured near the present limit, mixing-dependent CP-violation could become maximal. For electroweak penguin modes, the fourth generation can provide the enhancement that perhaps may be needed, while the m(l+l-) dependence of the forward-backward asymmetry in B --> K*l(+)l(-) can further probe for the fourth generation. These effects can be studied in detail at the B factories and the Tevatron.