Improving bounds on penguin pollution in B→ππ

Abstract

In the presence of penguin contributions, the indirect CP asymmetry in B 0 ( t )→ π + π − measures sin(2 α +2 θ ), where 2 θ parametrizes the size of the penguin “pollution”. We derive a new upper bound on |2 θ |, requiring the measurement of BR ( B + → π + π 0 ) and an upper bound on B 00 ≡ 1 2 [BR(B 0 →π 0 π 0 )+BR( B 0 →π 0 π 0 )] . The new bound is stronger than those previously discussed in the literature. We also present a lower bound on B 00 . Current data may suggest that it is not very small, in which case θ can be determined using a complete isospin analysis.