Difficulties in Obtaining Weak Phases from $b\to d$ Penguin Decays

Abstract

We re-examine a recent proposal for obtaining βusing the measurements of the b -> d penguin decays B_d(t) -> K^0 \kbar and B_s(t) -> ϕK_S, along with a theoretical assumption. We show that there are in fact three assumptions one can make, so that the method can in principle be used to extract α, βor γ. We also show that it is the assumption which yields γwhich is the best. However, the theoretical error on this assumption is still 25-30%, which leads to an error on γof at least 20-25%. Given our current understanding of hadronic physics, it does not seem possible to reduce this error.

14 pages, LaTeX, no figures. Paper shortened slightly; some additional explanations included; conclusions unchanged