Strong Penguin Research Articles

The influence of penguin activity on soil diatom assemblages on King George Island, Antarctica with the description of a new Luticola species.

BackgroundIce-free areas in the Antarctic region are strongly limited. The presence of marine mammals and birds in those areas influence soil properties and vegetation composition. Studies on the terrestrial diatom flora in soils influenced by sea birds in the Maritime Antarctic region are scarce.MethodsSamples were collected from two transects on the western shore of the Admiralty Bay region. Light and scanning electron microscopic observations and statistical analyses were conducted to consider the impact of penguin rookeries on soil diatom assemblages.ResultsThe disturbance associated with the presence of penguin rookeries clearly influences the soil diatom diversity. Assemblages from areas with the highest nutrient input were characterized by a much lower diversity with only few species dominating the flora. One of recorded taxa could not be assigned to any of the known species. Therefore, based on the combination of morphological features analyzed using light and scanning electron microscopes and comparison with similar taxa in the Antarctic region and worldwide, the species is described hereby as new to science–Luticola kaweckae sp.nov. The new species is characteristic for soil habitats with strong penguin influence.

Model-independent analysis of CP violation in charmed meson decays

We present a model-independent analysis of CP violation, inspired by recent experimental observations, in charmed meson decays. The topological diagram approach is used to study direct CP asymmetries for singly Cabibbo-suppressed two-body hadronic decays of charmed mesons. We extract the magnitudes and relative phases of the corresponding topological amplitudes from available experimental information. In order to get more precise and reliable estimates of direct CP asymmetries, we take into account contributions from all possible strong penguin amplitudes, including the internal [Formula: see text]-quark penguin contributions. We also study flavor SU(3) symmetry breaking effects in these decay modes and consequently predict direct CP asymmetries of unmeasured modes.

Spatial variability models of CO2 emissions from soils colonized by grass (Deschampsia antarctica) and moss (Sanionia uncinata) in Admiralty Bay, King George Island

AbstractSoil CO2 emission is an important part of the terrestrial carbon cycling and is influenced by several factors, such as type and distribution of vegetation. In this work we evaluated the spatial variability of soil CO2 emission in terrestrial ecosystems of maritime Antarctica, under two contrasting vegetation covers: 1) grass areas of Deschampsia antarctica Desv., and 2) moss carpets of Sanionia uncinata (Hedw.) Loeske. Highest mean emission was obtained for the Deschampsia (4.13 μmol m-2 s-1) developed on organic-rich soil with a strong penguin influence. The overall results indicate that soil temperature is not directly related to the spatial pattern of soil CO2 emission at the sites studied. Emission adjusted models were Gaussian and exponential with ranges varying from 1.3 to 2.8 m, depending on the studied site and vegetation cover.

Systematic effects of the quenched approximation on the strong penguin contribution toϵ′/ϵ

We discuss the implementation and properties of the quenched approximation in the calculation of the left-right, strong penguin contributions (i.e. ${Q}_{6}$) to ${ϵ}^{\ensuremath{'}}/ϵ$. The coefficient of the new chiral logarithm, discovered by Golterman and Pallante, which appears at leading order in quenched chiral perturbation theory is evaluated using both the method proposed by those authors and by an improved approach which is free of power divergent corrections. The result implies a large quenching artifact in the contribution of ${Q}_{6}$ to ${ϵ}^{\ensuremath{'}}/ϵ$. This failure of the quenched approximation affects only the strong penguin operators and so does not affect the ${Q}_{8}$ contribution to ${ϵ}^{\ensuremath{'}}/ϵ$ nor $\mathrm{Re}{A}_{0}$, $\mathrm{Re}{A}_{2}$ and thus, the $\ensuremath{\Delta}I=1/2$ rule at tree level in chiral perturbation theory.

Quenched penguin operators and theΔI=1/2rule

The transformation properties of strong penguin operators under the action of the flavor group change when they are considered as operators in (partially) quenched QCD instead of the unquenched theory. As a result, additional operators and new low-energy constants appear in the effective theory describing nonleptonic kaon decay matrix elements in the partially quenched setting. These new low-energy constants do not have a counterpart in the unquenched theory, and should thus be considered as an artifact of the quenched approximation. Here we consider strong penguin operators consisting of products of two left-handed flavor currents, and give a complete one-loop analysis in the effective theory for ${K}^{0}$ to vacuum and ${K}^{+}$ to ${\ensuremath{\pi}}^{+}$ matrix elements. We find that the new low-energy constants already appear in these matrix elements at leading order. This implies that (partially) quenched lattice computations of for instance the $\ensuremath{\Delta}I=1/2$ rule are affected by ambiguities intrinsic to the use of the quenched approximation at leading order. The only exception is the partially quenched case with three light sea quarks, consistent with general expectations. Our results are also relevant when the charm quark is kept in the theory.

ReexaminingB→ππ,πKdecays in QCD factorization approach

Motivated by the recent experimental data, we have revisited the $B\to \pi K,\pi \pi$ decays in the framework of QCD factorization, with inclusion of the important strong penguin corrections of order $\alpha_s^2$ induced by $b\to D g^\ast g^\ast$ ($D=d$ or $s$ and $g^\ast$ denotes an off-shell gluon) transitions. We find that these higher order strong penguin contributions can provide $\sim 30%$ enhancement to the penguin-dominated $B\to \pi K$ decay rates, and such an enhancement can improve the consistency between the theoretical predictions and the experimental data significantly, while for the tree-dominated $B\to \pi\pi$ decays, these higher order contributions play only a minor role. When these strong penguin contributions are summed, only a small strong phase remains and the direct CP asymmetries get small corrections. We also find patterns of the ratios between the CP-averaged branching fractions remain nearly unaffected even after including these higher order corrections and the $\pi K$ puzzle still persists. Our results may indicate that to resolve the puzzle one would have to resort to new physics contributions in the electroweak penguin sector as found by Buras {\it et al}.

Quenching effects in strong penguin contributions to [formula omitted

Quenching effects in strong penguin matrix elements are investigated. A lattice determination of αqNS, the constant that appears in the quenched ChPT relevant for the lattice analysis of K→ππ matrix elements, shows that this constant is large. The original RBC analysis of Q6 matrix elements is revisited in light of this result. Also, the numerical effects of choosing the singlet Golterman-Pallante method of quenching Q6 is investigated.

Unfactorizing Polychromatic Penguins

Firstly, I report on a recent work --carried out with T. Hambye and E. de Rafael-- on how to use the large-Nc expansion to calculate unfactorized contributions from the strong penguin operators, and their impact on observables such as epsilon'/epsilon and the Delta I = 1/2 rule. Secondly, based on work done with M. Golterman, I explain how this calculation allows one to predict some rather dramatic consequences for quenched QCD. This may help explain the present discrepancy between lattice and experimental results for epsilon'/epsilon. The emphasis of this article is put on the explanation of the method of calculation used, which is fully analytic. This allows one to build some intuition and understand the role played by the different hadronic scales in determining the size of the different contributions.

Effects of (partial) quenching on penguin contributions toK→ππ

Recently, we pointed out that chiral transformation properties of strong penguin operators change in the transition from unquenched to (partially) quenched QCD. As a consequence, new penguinlike operators appear in the (partially) quenched theory, along with new low-energy constants, which should be interpreted as a quenching artifact. Here, we extend the analysis of the contribution of the new low-energy constants to the ${K}^{0}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ amplitude, at leading order in chiral perturbation theory, and for arbitrary (momentum nonconserving) kinematics. Using these results, we provide a detailed discussion of the intrinsic systematic error due to this (partial) quenching artifact. We also give a simple recipe for the determination of the leading-order low-energy constant parametrizing the new operators in the case of strong LR penguins operators.

Analytic estimates of quenched penguins

Abstract When we embed the strong penguin operator Qs in the quenched theory, it does not remain a singlet under right-handed chiral transformations. As a consequence, more low-energy constants associated with this operator appear than in the unquenched theory. We give analytic estimates of the leading constants. The results suggest that the effects of quenching on this operator are large.

Effects of new physics on CP violation in B decays

We discuss two models with 1 extra CP phase in $b\leftrightarrow s$ transition. The CP phase $\arg (V_{t^\prime s}V_{t^\prime b})$ with fourth generations, previously ignored, could impact on $b\to s\ell^+\ell^-$, $\Delta m_{B_s}$ and $\sin2\Phi_{B_s}$, but does not affect EM and strong penguins. With SUSY at TeV scale, a right-handed ``$\widetilde{sb}_{1}$'' squark can be driven light by flavor mixing. It does not affect $b\to s\ell^+\ell^-$, but can generate $S_{\phi K_S} < 0$ while giving $S_{\eta^\prime K_S} \sim \sin2\Phi_{B_d} \cong0.74$. $B_s$ mixing and $\sin2\Phi_{B_s}$ would likely be large, and $S_{K_S\pi^0\gamma}\neq 0$ in $B^0\to K^{*0}\gamma$ is promising.

Analytic estimates for penguin operators in quenched QCD

Strong penguin operators are singlets under the right-handed flavor symmetry group $\mathrm{SU}{(3)}_{R}.$ However, they do not remain singlets when the operator is embedded in (partially) quenched QCD, but instead they become linear combinations of two operators with different transformation properties under the (partially) quenched symmetry group. This is an artifact of the quenched approximation. Each of these two operators is represented by a different set of low-energy constants in the chiral effective theory. In this paper, we give analytic estimates for the leading low-energy constants, in quenched and partially quenched QCD. We conclude that the effects of quenching on ${Q}_{6}$ are large.

Effect of fourth generation CP phase on $b\to s$ transitions

We study the effect of a sequential fourth generation on b\to s gamma, B_s mixing, B\to K^{(*)}\ell^+\ell^-, X_s\ell^+\ell^- and \phi K_S, taking into account the presence of a new CP phase in quark mixing. We find that the effects via electromagnetic and strong penguins, such as in b\to s gamma or CP violation in B\to \phi K_S, are rather mild, but impact via box or Z penguins is quite significant. Not only can one have much larger than expected B_s mixing, even if it is measured near the present limit, mixing dependent CP violation could become maximal. For electroweak penguin modes, the fourth generation can provide the enhancement that perhaps may be needed, while the m_{\ell^+\ell^-} dependence of the forward-backward asymmetry in B\to K^{*}\ell^+\ell^- can further probe for the fourth generation. These effects can be studied in detail at the B factories and the Tevatron.

Semi-inclusive decayB→φXs:Rate and momentum spectrum ofφ

We study the rate and $\ensuremath{\varphi}$ momentum distribution in semi-inclusive decays $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{X}_{s}$ induced by the quark level processes $\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}s$ and $\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}sg,$ in which the gluon is radiated from the internal charm quark loop or emitted from the virtual gluon of the strong penguin (inner bremsstrahlung) process. We find $\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}s)=6.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ and $\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}sg)=3.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}.$ The momentum spectrum of $\ensuremath{\varphi}$ produced by $\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}\mathrm{sg}$ is very broad. With the cut $|{\mathbf{k}}_{\ensuremath{\varphi}}|&gt;~2.0\mathrm{GeV},$ $\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}s)=6.1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ (where the Fermi motion of the b quark in the B meson is described by a Gaussian), and $\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{b}\ensuremath{\varphi}sg)=1.0\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}.$ Because of the special nature of $\ensuremath{\varphi},$ many difficulties that hindered a reliable theoretical prediction for $\stackrel{\ensuremath{\rightarrow}}{B}{\ensuremath{\eta}}^{\ensuremath{'}}{X}_{s}$ decay are absent in the process $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{X}_{s}.$ Therefore, theoretical predictions for $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{X}_{s}$ are relatively clean. Moreover, the clear experimental signature of the $\ensuremath{\varphi}$ is of great help. Data for $\stackrel{\ensuremath{\rightarrow}}{B}\ensuremath{\varphi}{X}_{s},$ both the branching ratio and the $\ensuremath{\varphi}$ momentum distribution, would teach us about the strength of strong penguin processes which might be of great importance in the search for $\mathrm{CP}$ violation and for new physics at B factories.

B → Kπ decays and the weak phase angle γ

The large branching ratios for B → Kπ decays as observed by the CLEO Collaboration indicate that penguin interactions contribute a major part to the decay rates and provide an interference between the Cabibbo-suppressed tree and penguin contributions resulting in a CP-asymmetry between the B → Kπ and its charge conjugate mode. The CP-averaged decay rates depend also on the weak phase γ and give us a determination of this phase. In this talk, I would like to report on a recent analysis of B → Kπ decays using factorisation model with final state interaction phase shift included. We find that factorisation seems to describe qualitatively the latest CLEO data. We also obtain a relation for the branching ratios independent of the strength of the strong penguin interactions. This relation gives a central value of 0.60 × 10 −5 for B( B̄ 0 → K̄ 0π 0), somewhat smaller than the latest CLEO measurement. We also find that a ratio obtained from the CP-averaged B → Kπ decay rates could be used to test the factorisation model and to determine the weak angle γ with more precise data, though the latest CLEO data seem to favor γ in the range 90° – 120°.

B→ππ,Kπdecays in the QCD improved factorization approach

Motivated by recent measurements, we investigate $B\to \pi \pi, K \pi$ decay modes in the framework of QCD improved factorization, which was recently proposed by Beneke $et al$. We find that all the measured branching ratios are well accommodated in the reasonable parameter space except for $B\to K^0 \pi^0 $. We also discuss in detail the strong penguin contributions and the ${\cal O}(\alpha_s)$ corrections to the chirally enhanced terms. We find that the weak phase $\gamma$ lies in the region $120^{\circ}<\gamma<240^{\circ}$, which is mainly constrained by $B\to \pi^- \pi^+ $.

Test of factorization inB→Kπdecays

We analyze the $\stackrel{\ensuremath{\rightarrow}}{B}K\ensuremath{\pi}$ decays using the factorization model with the final state interaction phase shift included. We find that factorization seems to describe qualitatively the latest CLEO data. For a test of the factorization model, we derive a relation for the branching ratios independent of the strength of the strong penguin interactions. This relation gives a central value of $(0.60\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5})$ for $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{K}^{0}{\ensuremath{\pi}}^{0}),$ somewhat smaller than the latest CLEO measurement, but the experimental errors are yet too big to take it as a real prediction of the factorization model. We also find that a ratio obtained from the $\mathrm{CP}$-averaged $\stackrel{\ensuremath{\rightarrow}}{B}K\ensuremath{\pi}$ decay rates could be used to test the factorization model and to determine the weak angle \ensuremath{\gamma} with more precise data, although the latest CLEO data seem to favor \ensuremath{\gamma} in the range of (90\ifmmode^\circ\else\textdegree\fi{}--120\ifmmode^\circ\else\textdegree\fi{}).

Penguin operators in nonresonantB−→MM¯π−(M=π−,K−,K0)decays

We investigate the contributions coming from the penguin operators in the nonresonant $B^- \to M \bar M \pi^-$ ($M =\pi^-, K^-, K^0$) decays. The effective Wilson coefficients of the the strong penguin operators $O_{4,6}$ are found to be relatively larger. We calculate the contributions arising from the $O_4$ and $O_6$ operators in the nonresonant decays $B^- \to M \bar M\pi^-$ ($M = \pi^-, K^-, \bar K^0$) using a model combining heavy quark symmetry and the chiral symmetry, developed previously. We find that the forbidden nonresonant $B^- \to K^0 \bar K^0 \pi^-$ decay occurs through the strong penguin operators. These penguin contributions affect the branching ratios for $B^- \to M \bar M\pi^-$ ($M = \pi^-, K^-$) by only a few percent. The branching ratio for $B^- \to K^0 \bar K^0 \pi^-$ is estimated to be of the order $ 10^{-6}$.

A simplified approach to determine α and the penguin amplitude in Bd → ππ

The effect of inelastic final-state interactions (IFSIs) on the determination of the weak phase α from the isospin triangles of B → ππ is qualitatively illustrated. Neglecting the electroweak penguins and IFSIs and assuming the dominance of the top-quark loop in strong penguin diagrams, we propose an experimentally accessible way to approximately determine α and the penguin amplitude in B d → ππ. This approach relies on a simplified isospin consideration and the factorization approximation, and its feasibility is irrelevant to the time-dependent measurements of B d → ππ.

Isospin structure of penguin diagrams and their consequences in B meson physics.

Isospin structure of gluon mediated or strong penguin is significantly altered when the full electroweak corrections are included. This has the consequence that some previous analyses which relied on a simple isospin structure in charmless $B$ decays become inapplicable. We present the general Hamiltonian in next-to-leading order QCD, and illustrate our conclusion quantitatively for $B\rightarrow \pi\pi$ and $B\rightarrow K\pi$ decays in the factorization approximation. Some remarks on CP asymmetries in $B$ decays are also made.