Penguin Pollution in B->pi pi

A reliable prediction for $CP$ violation in $B^{0}_{d}$ vs $\bar{B}^{0}_{d}\rightarrow \pi^{+}\pi^{-}$ suffers from the penguin-diagram induced uncertainty. With the help of SU(3) relations, we show that both the magnitude and strong phase shift of the penguin amplitude can be approximately determined only from the branching ratios of $B^{0}_{d}\rightarrow \pi^{+}\pi^{-}$, $B^{0}_{d}\rightarrow K^{+}\pi^{-}$, and $B^{+}_{u}\rightarrow K^{0}\pi^{+}$.

The decays $B_d\to\pi^+\pi^-$ and $B_s\to K^+K^-$ provide an interesting strategy to extract the CKM angle $\gamma$ at ``second-generation'' $B$-physics experiments of the LHC era. A variant for ``first-generation'' experiments can be obtained, if $B_s\to K^+K^-$ is replaced by $B_d\to\pi^\mp K^\pm$. We show that the most recent experimental results for the CP-averaged $B_d\to\pi^+\pi^-$ and $B_d\to\pi^\mp K^\pm$ branching ratios imply a rather restricted range for the corres...

The role of penguin amplitudes in CP violating $B$ decays is reviewed, emphasizing recent progress in the analysis of electroweak penguin contributions. It is shown how these terms are included in a model-independent manner when measuring the weak phase $\alpha$ in $B\to\pi\pi$ using isospin symmetry, and when determining the phase $\gamma$ from $B\to K\pi$ applying flavor SU(3). Uncertainties due to rescattering effects in $B\to K\pi$ are discussed.

The $B\to\pi K$ decays with significant electroweak penguin contributions show a puzzling pattern. We explore this "$B\to\pi K$ puzzle" through a systematic strategy. The starting point, which is essentially unaffected by electroweak penguins, is the determination of the angle $\gamma$ of the unitarity triangle through the CP-violating $B^0_d\to\pi^+\pi^-$, $B^0_d\to\pi^-K^+$ asymmetries, yielding $\gamma=(73.9^{+5.8}_{-6.5})^\circ$, and the extraction of hadronic parameters ...

We reanalyze the decay $B_d\to\pi^+\pi^-$ without assuming dominance of QCD penguins with internal top-quark exchanges. In that case the weak phase of the $\bar b \to\bar d$ QCD penguin amplitude is not related in a simple way to the CKM angle $\beta$. Nevertheless it is still possible to extract the CKM angle $\alpha$ in a transparent and almost model-independent way from the time-dependent CP-violating asymmetry of the transition $B_d\to\pi^+\pi^-$. Aside from that CP asymm...

Theoretically motivated smallness of the penguin amplitude in $B \to \pi \pi$ decays allowes to calculate the value of the unitarity triangle angle $\alpha (\phi_2)$ with good accuracy. The relatively large branching ratio of the decay into $\pi^0 \pi^0$ is explained by the large value of FSI phase difference between $\Delta I = 1/2$ and $\Delta I = 3/2$ tree amplitudes.

A major goal in B physics is measuring the CP-violating asymmetry in the decay $B^0 \rightarrow \pi^+ \pi^-$. In order to determine one of the phase angles in the CKM matrix from this decay it is necessary to determine the influence of the penguin amplitude. Here we show how, using $SU(3)$ symmetry, the penguin effect can be approximately determined from the ratio of the decay rates of $B^0 \rightarrow K^+ \pi^-$ and $B^0 \rightarrow \pi^+ \pi^-$.

Over the last two decades, $B \to \pi K$ modes have received a lot of attention. They are particularly interesting since the main contribution to these decays comes from QCD penguin topologies. Furthermore, electroweak penguin amplitudes enter at a level comparable to the tree topologies. In the past, a discrepancy was found in the correlation between the CP asymmetries of $B_d^0 \to \pi^0 K_{\rm S}$. We provide the state-of-the-art picture of this situation and consider new ...

We show how B -> pi pi decays can be used to search for new physics in the b -> d flavour-changing neutral current. One needs one piece of theoretical input, which we take to be a prediction for P/T, the ratio of the penguin and tree amplitudes in Bd -> pi+ pi-. If present, new physics can be detected over most of the parameter space. If \alpha (\phi_2) can be obtained independently, measurements of B+ -> pi+ pi0 and Bd/Bd(bar) -> pi0 pi0 are not even needed.

We show that the anomalies in the $B\to\pi\pi$ decay channels, {\em viz.}, the large branching ratio of $B\to\pi^0\pi^0$ and large direct CP asymmetry of $B\to\pi^+\pi^-$, can both be explained, even in the framework of existing theoretical models which predict the relative strengths of the tree and the strong penguin amplitudes, if there is an abnormally large electroweak penguin contribution. We also critically examine the expectation of a similarly large electroweak pengui...