Electroweak Penguin Contributions Research Articles

Angular distribution and direct CP violation with perturbative strong phases in B → W decays

Angular distribution and direct CP violation in B → W decays are calculated with perturbative strong phases from both electroweak and QCD penguins. Electroweak penguin contributions are found to be large and can change the interference terms in angular distributions significantly. We comment on the use of factorization approximation and q 2 uncertainty in penguins.

Electroweak penguin diagrams and two-body B decays.

We discuss the role of electroweak penguins in $B$ decays to two light pseudoscalar mesons. We confirm that the extraction of the weak phase $\alpha$ through the isospin analysis involving $B\to\pi\pi$ decays is largely unaffected by such operators. However, the methods proposed to obtain weak and strong phases by relating $B\to\pi\pi$, $B\to\pi K$ and $B\to KK$ decays through flavor SU(3) will be invalidated if electroweak penguins are large. We show that, although the introduction of electroweak penguin contributions introduces no new amplitudes of flavor SU(3), there are a number of ways to experimentally measure the size of such effects. Finally, using SU(3) amplitude relations we present a new way of measuring the weak angle $\gamma$ which holds even in the presence of electroweak penguins.

Unique signature of electroweak penguin in pure hadronic B decays

We study electroweak penguin contributions in pure hadronic B decays in the Standard and two-Higgs-doublet models. We find that in B s → π 0( ν, φ) and B s → ϱ 0 ( ν, φ) decays the electroweak penguin contributions dominate over all other contributions. These processes provide unique signatures of electroweak penguin in pure hadronic processes. These modes could be in measurable range of future B facilities.

Limitations in measuring the angle β by using SU(3) relations for B-meson decay-amplitudes

Flavour SU(3) symmetry of strong interactions and certain dynamical assumptions have been used in a series of recent publications to extract weak CKM phases from B-decays into {ππ, πK, K K ̄ } final states. We point out that irrespectively of SU(3)-breaking effects the presence of QCD-penguin contributions with internal u- and c-quarks precludes a clean determination of the angle β in the unitarity triangle by using the branching ratios only. This difficulty can be overcome by measuring in addition the ratio x d / x s of B d 0− B ̄ d 0 to B s 0− B ̄ s 0 mixings. The measurement of the angle γ is unaffected by these new contributions. Some specific uncertainties related to SU(3)-breaking effects and electroweak penguin contributions are briefly discussed.

Limitations in measuring the angle β by using SU(3) relations for B-meson decay-amplitudes

Flavour $SU(3)$ symmetry of strong interactions and certain dynamical assumptions have been used in a series of recent publications to extract weak CKM phases from $B$-decays into $\{\pi\pi,\pi K, K\bar K\}$ final states. We point out that irrespectively of $SU(3)$-breaking effects the presence of QCD-penguin contributions with internal $u$- and $c$-quarks precludes a clean determination of the angle $\beta$ in the unitarity triangle by using the branching ratios only. This difficulty can be overcome by measuring in addition the ratio $x_d/x_s$ of $B^0_d-\bar B^0_d$ to $B^0_s-\bar B^0_s$ mixings. The measurement of the angle $\gamma$ is unaffected by these new contributions. Some specific uncertainties related to $SU(3)$-breaking effects and electroweak penguin contributions are briefly discussed.

Search for the angle γ in the electroweak penguin dominated decay Bs→ π0Φ

We point out that due to the isospin symmetry of strong interactions, QCD penguins do not contribute to B s → π 0 Φ. However, since the current-current amplitude A CC is both CKM- and colour-suppressed, the electroweak penguin contribution A EWP becomes important and even dominant. The CP asymmetry A CP arising in B s → π 0 Φ is expressed as a function of x≡ A EWP/ A CC and of the angle γ ≡ −arg( V ub ) and is a rather clean measure of this CKM-phase, since the hadronic uncertainties affecting x can be absorbed through the colour-suppression factor a 2. Since, moreover, BR( B s → π 0 Φ) = O(10 −7) be of comparable size as BR( B s → ϱ 0 K S ), we suggest that B s → π 0 Φ may be a promising mode to extract γ.