Measuring Arg(Vub) in B → Kπ

It has previously been shown that a measurement of Arg(Vub) = can be obtained from a triangle construction using B(B 0 → K + � − ), B( ¯ B 0 → K − � + ), B(B ± → K 0 s � ± ), and B(B ± → � ± � 0 ). We evaluate experimental as well as theoretical uncertainties in this measurement. We find that a measurement of with the next generation B-factories (BaBar, BELLE, CLEO III) is statistics rather than theory limited if soft rescattering effects are small.