If new physics (NP) is present in $B\to \pi \pi$ decays, it can affect the isospin $I=2$ or $I=0$ channels. In this paper, we discuss various methods for detecting and measuring this NP. The techniques have increasing amounts of theoretical hadronic input. If NP is eventually detected in $B\to \pi \pi$—there is no evidence for it at present—one will be able to distinguish $I=2$ and $I=0$, and measure its parameters, using these methods.

• Received 6 October 2005

DOI:https://doi.org/10.1103/PhysRevD.72.114007