Penguin Diagrams Research Articles

Nonresonant three-body decays of B to J/ψππ

We investigate the nonresonant three-body decays of the B meson to J/ψπ+π− and J/ψπ+π0 final-states mesons. There are a tree and a penguin diagram for these decays modes in the naive factorization approach. The transition matrix element of is factorized into a form factor multiplied by the J/ψ decay constant. We assume that the J/ψ meson remains stationary and the two pion mesons move back to back. We calculate the branching ratio of the and decays and obtain 1.09 × 10−5 and 5.45 × 10−6, respectively, while the experimental results are less than 1.2 × 10−5 and 7.3 × 10−6, respectively. The branching ratios obtained in our model, are compatible with the upper limits of the experimental results.

Enhancingli→3ljwith theZ0-penguin

Lepton flavor violation has been observed in neutrino oscillations. For charged lepton flavor violation decays only upper limits are known, but sizable branching ratios are expected in many neutrino mass models. High-scale models, such as the classical supersymmetric seesaw, usually predict that decays ${l}_{i}\ensuremath{\rightarrow}3{l}_{j}$ are roughly a factor $\ensuremath{\alpha}$ smaller than the corresponding decays ${l}_{i}\ensuremath{\rightarrow}{l}_{j}\ensuremath{\gamma}$. Here we demonstrate that the ${Z}^{0}$-penguin diagram can give an enhancement for decays ${l}_{i}\ensuremath{\rightarrow}3{l}_{j}$ in many extensions of the minimal supersymmetric standard model (MSSM). We first discuss why the ${Z}^{0}$-penguin is not dominant in the MSSM with seesaw and show that much larger contributions from the ${Z}^{0}$-penguin are expected in general. We then demonstrate the effect numerically in two example models, namely, the supersymmetric inverse seesaw and $R$-parity violating supersymmetry.

Enhanced Higgs mediated lepton flavour violating processes in the supersymmetric inverse seesaw model

Abstract We study the impact of the inverse seesaw mechanism on several low-energy flavour violating observables such as τ → μμμ in the context of the Minimal Supersymmetric Standard Model. As a consequence of the inverse seesaw, the contributions of the right-handed sneutrinos significantly enhance the Higgs-mediated penguin diagrams. We find that different flavour violating branching ratios can be enhanced by as much as two orders of magnitude. We also comment on the impact of the Higgs-mediated processes on the leptonic B-meson decays and on the Higgs flavour violating decays.

Penguin and box diagrams in unitary gauge

We evaluate one-loop diagrams in the unitary gauge that contribute to flavor-changing neutral current (FCNC) transitions involving two and four fermions. Specifically, we deal with penguin and box diagrams arising within the standard model (SM) and in nonrenormalizable extensions thereof with anomalous couplings of the W boson to quarks. We show explicitly in the SM the subtle cancelation among divergences from individual unitary-gauge contributions to some of the physical FCNC amplitudes and derive expressions consistent with those obtained using R_xi gauges in the literature. Some of our results can be used more generally in certain models involving fermions and gauge bosons which have interactions similar in form to those we consider.

Branching ratio and CP violation of B c →DK decays in the perturbative QCD approach

In this paper, we calculate the branching ratio and direct CP asymmetry parameter of $B_c^{\pm}\to D^{0}K^{\pm}$ in the framework of perturbative QCD approach based on $k_T$ factorization. Besides the usual factorizable diagrams, both non-factorizable and annihilation type contributions are taken into account. We find that (a) the branching ratio is at the order of $10^{-5}$; (b) the tree annihilation diagrams and the penguin diagrams dominate the total contribution; and (c) the direct CP asymmetry is about 7%, which can be tested in the Large Hadron Collider beauty experiments (LHC-b) at CERN.

Analysis of the rare semileptonic decays ofBstof0(980)andK0*(1430)scalar mesons in QCD sum rules

We investigate the rare semileptonic decays ${B}_{s}\ensuremath{\rightarrow}[{f}_{0}(980),{K}_{0}^{*}(1430)]{l}^{+}{l}^{\ensuremath{-}}$, ($l=e$, $\ensuremath{\mu}$, $\ensuremath{\tau}$), and ${B}_{s}\ensuremath{\rightarrow}[{f}_{0}(980),{K}_{0}^{*}(1430)]\ensuremath{\nu}\overline{\ensuremath{\nu}}$ in the framework of the three-point QCD sum rules. These decays are important to study because the ${f}_{0}(980)$ and ${K}_{0}^{*}(1430)$ are the scalar mesons with total spin 0 and even parity and the quark content of them are still controversial in high energy physics. These rare decays occur at loop level by electroweak penguin and weak box diagrams in the standard model via the flavor changing neutral current transitions of $b\ensuremath{\rightarrow}d$, $s$, and not allowed by tree level. Considering the effective contributions of the nonperturbative parts of the correlation function, we calculate the relevant form factors of these transitions. The branching fractions and longitudinal lepton polarization asymmetry are also investigated.

Investigation of the Ds1 structure via Bc to transitions in QCD

We investigate the structure of the Ds1(2460, 2536)(JP = 1+) mesons via analyzing the semileptonic Bc → Ds1l+l−, l = τ, μ, e and transitions in the framework of the three-point QCD sum rules. We consider the Ds1 meson in two ways, the pure state and then as a mixture of two |3P1⟩ and |1P1⟩ states. Such types of rare transitions take place at loop level by electroweak penguin and weak box diagrams in the standard model via the flavor changing neutral current transition of b → s. The relevant form factors are calculated taking into account the gluon condensate contributions. These form factors are numerically obtained for case and plotted in terms of the unknown mixing angle θs, when the Ds1 meson is considered as a mixture of two |3P1⟩ and |1P1⟩ states. The obtained results for the form factors are used to evaluate the decay rates and branching ratios. Any future experimental measurement on these form factors as well as decay rates and branching fractions and their comparison with the obtained results in the present work can give considerable information about the structure of this meson and the mixing angle θs.

Complete one-loop MSSM predictions forB0→ℓ+ℓ′−at the Tevatron and LHC

During the last few years the Tevatron has dramatically improved the bounds on rare $B$-meson decays into two leptons. In the case of ${B}_{s}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$, the current bound is only 10 times greater than the standard model expectation. Sensitivity to this decay is one of the benchmark goals for LHCb performance and physics. The Higgs penguin dominates this rate in the region of large $\mathrm{tan}\ensuremath{\beta}$ of the minimal supersymmetric standard model. This is not necessarily the case in the region of low $\mathrm{tan}\ensuremath{\beta}$, since box and $Z$-penguin diagrams may contribute at a comparable rate. In this article, we compute the complete one-loop minimal supersymmetric standard model contribution to ${B}_{s,d}^{0}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{'}\ensuremath{-}}$ for $\ensuremath{\ell}$, ${\ensuremath{\ell}}^{\ensuremath{'}}=e$, $\ensuremath{\mu}$. We study the predictions for general values of $\mathrm{tan}\ensuremath{\beta}$ with arbitrary flavor mixing parameters. We discuss the possibility of both enhancing and suppressing the branching ratios relative to their standard model expectations. In particular, we find that there are ``cancellation regions'' in parameter space where the branching ratio is suppressed well below the standard model expectation, making it effectively invisible to the LHC.

Search for TeV scale physics in heavy flavor decays

The subject of heavy flavor decays as probes for physics at and beyond the TeV scale is covered from the experimental perspective. Emphasis is placed on the more traditional beyond the standard model topics that have potential for impact in the early LHC era, and that are in anticipation of the B factory upgrade(s). The aim is to explain the physics, without getting too involved in the details, whether experimental or theoretical, to give the interested non-expert a perspective on the flavor/TeV link. We cover the forefront topics of CP violation in b→s transitions involving penguin and box diagrams, and probes of charged Higgs, right-handed and scalar interactions. We touch briefly on ϒ decay, D 0 mixing, rare K decays, and lepton flavor violating probes in τ decay. Our own phenomenological work is often used for illustration.

CP-conserving unparticle phase effects on the unpolarized and polarized directCPasymmetry inb→dl+l−transition

We examine the unparticle $CP$-conserving phase effects on the direct $CP$ asymmetry for both polarized and unpolarized leptons in the inclusive $b\ensuremath{\rightarrow}d{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ transition, where the flavor-changing neutral currents are forbidden at tree level but are induced by one-loop penguin diagrams. The averaged polarized and unpolarized $CP$ asymmetries depict strong dependency on the unparticle parameters. In particular, a sizable discrepancy corresponding to the standard model is achieved when the scale dimension value is $1<{d}_{\mathcal{U}}<2$. We see that the unparticle stuff significantly enhances, suppresses, or changes the sign of the $CP$ asymmetry depending on the definite value of the scaling dimension ${d}_{\mathcal{U}}$. Especially, when ${d}_{\mathcal{U}}\ensuremath{\sim}1.1$ the $CP$ asymmetries vanish.

B-physics prospects with the LHCb experiment

This paper summarizes the B-physics prospects of the LHCb experiment. Firstly, a brief introduction to the CKM matrix and the mechanism of CP violation in the Standard Model is given. The advantages of the LHCb experiment for B-physics exploitation will then be described, together with a short description of the detector components. Finally, the LHCb physics aims and prospects will be summarized, focusing on the measurements of sin(2β) in tree and gluonic penguin diagrams, sin(2α) in Bd0 → π+π− and π+π−π0, neutral B-meson oscillations and the Bs0 mixing phase, and the measurement of γ using a variety of complementary methods.

Pseudoscalar and scalar operators of Higgs penguin diagrams in the MSSM andB→ϕK*,Kη(′)decays

We study the effect of $b\ensuremath{\rightarrow}s\overline{s}s$ scalar/pseudoscalar operators in $B\ensuremath{\rightarrow}K{\ensuremath{\eta}}^{(\ensuremath{'})}$, $\ensuremath{\phi}{K}^{*}$ decays. In the minimal supersymmetric standard model (MSSM), such scalar/pseudoscalar operators can be induced by the penguin diagrams of neutral-Higgs bosons. These operators can be Fierz-transformed into tensor operators, and the resultant tensor operators could affect the transverse polarization amplitudes in $B\ensuremath{\rightarrow}\ensuremath{\phi}{K}^{*}$ decays. A combined analysis of the decays $B\ensuremath{\rightarrow}\ensuremath{\phi}{K}^{*}$ and $B\ensuremath{\rightarrow}K{\ensuremath{\eta}}^{(\ensuremath{'})}$, including $b\ensuremath{\rightarrow}s\overline{s}s$ scalar/pseudoscalar operators and their Fierz-transformed tensor operators originated from the MSSM, is performed. Our study is based on the following: (1) Assuming that weak annihilations in $B\ensuremath{\rightarrow}\ensuremath{\phi}{K}^{*}$ are negligible and the polarization puzzle is resolved by Fierz-transformed tensor operators, it results in too large coefficients of scalar/pseudoscalar operators, such that the resulting $B\ensuremath{\rightarrow}K{\ensuremath{\eta}}^{(\ensuremath{'})}$ branching fractions are much larger than observations. (2) When we take the weak annihilations in $B\ensuremath{\rightarrow}\ensuremath{\phi}{K}^{*}$ into account, the polarization puzzle can be resolved. In this case, new physics effects are strongly suppressed and no more relevant to the enhancement of the transverse modes in $B\ensuremath{\rightarrow}\ensuremath{\phi}{K}^{*}$ decays.

RareKandBdecays in the littlest Higgs model without T-parity

We analyze rare K and B decays in the Littlest Higgs (LH) model without T-parity. We find that the final result for the Z^0-penguin contribution contains a divergence that is generated by the one-loop radiative corrections to the currents corresponding to the dynamically broken generators. Including an estimate of these logarithmically enhanced terms, we calculate the branching ratios for the decays K^+ -> pi^+ nu bar nu, K_L -> pi^0 nu bar nu, B_{s,d} -> mu^+ mu^- and B -> X_{s,d} nu bar nu. We find that for the high energy scale f=O(2-3) TeV, as required by the electroweak precision studies, the enhancement of all branching ratios amounts to at most 15% over the SM values. On the technical side we identify a number of errors in the existing Feynman rules in the LH model without T-parity that could have some impact on other analyses present in the literature. Calculating penguin and box diagrams in the unitary gauge, we find divergences in both contributions that are cancelled in the sum except for the divergence mentioned above.

Implications of new data in charmlessBdecays

Based on the latest experimental data of $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ and $\ensuremath{\pi}K$ modes, a model-independent analytical analysis is presented. The $CP$-averaged branching ratio difference $\ensuremath{\Delta}R={R}_{c}\ensuremath{-}{R}_{n}$ in $B\ensuremath{\rightarrow}\ensuremath{\pi}K$ decays with ${R}_{c}=2\mathrm{Br}({\ensuremath{\pi}}^{0}{K}^{\ensuremath{-}})/\mathrm{Br}({\ensuremath{\pi}}^{\ensuremath{-}}{\overline{K}}^{0})$ and ${R}_{n}=\mathrm{Br}({\ensuremath{\pi}}^{+}{K}^{\ensuremath{-}})/2\mathrm{Br}({\ensuremath{\pi}}^{0}{\overline{K}}^{0})$ is reduced though it remains larger than the prediction from the standard model (SM) as both measured ${R}_{n}$ and ${R}_{c}$ are enhanced, which indicates that a room for new physics becomes smaller. The present data of $\ensuremath{\pi}\ensuremath{\pi}$ decay reduce the ratio $|C/T|$ from the previous value of $|C/T|\ensuremath{\simeq}0.8$ to $|C/T|\ensuremath{\simeq}0.65$, which is still larger than the theoretical estimations based on QCD factorization and pQCD. Within SM and flavor SU(3) symmetry, the current $\ensuremath{\pi}K$ data also diminish the ratio $|{C}^{\ensuremath{'}}/{T}^{\ensuremath{'}}|$ from the previous value $|{C}^{\ensuremath{'}}/{T}^{\ensuremath{'}}|\ensuremath{\simeq}2$ to $|{C}^{\ensuremath{'}}/{T}^{\ensuremath{'}}|\ensuremath{\simeq}1.16$ with a large strong phase ${\ensuremath{\delta}}_{{C}^{\ensuremath{'}}}\ensuremath{\simeq}\ensuremath{-}2.65$, while its value remains much larger than the one extracted from the $\ensuremath{\pi}\ensuremath{\pi}$ modes. The direct $CP$ violation ${A}_{CP}({\ensuremath{\pi}}^{0}{\overline{K}}^{0})$ is predicted to be ${A}_{CP}({\ensuremath{\pi}}^{0}{\overline{K}}^{0})=\ensuremath{-}0.15\ifmmode\pm\else\textpm\fi{}0.03$, which is consistent with the present data. Two kinds of new effects in both strong and weak phases of the electroweak penguin diagram are considered. It is found that both cases can reduce the ratio to $|{C}^{\ensuremath{'}}/{T}^{\ensuremath{'}}|=0.40\ensuremath{\sim}0.80$ and lead to roughly the same predictions for $CP$ violation in ${\ensuremath{\pi}}^{0}{K}^{0}$.

Measurements of CP parameter at Belle

A precise determination of the CP parameter ϕ1(β) is the main purpose of the Belle experiment. The value was first measured for b→c transition decays and the CP violation in B meson decays was established. The measurement is now extended to b→s transition decays which are mediated by a penguin diagram. The measurement is sensitive to the existence of New Physics in the penguin loop. The results of latest measurements of ϕ1 at Belle are reported in this talk.

Analysis of a model with a common source of CP violation

We work in a model where all CP-violating phenomena have a common source. CP is spontaneously broken at a large scale V through the phase of a complex singlet scalar. An additional SU(2)L singlet vector-like down-type quark relates this high scale CP violation to low energy. We quantitatively analyse this model in the quark sector. We obtain the numerical values of the parameters of the Lagrangian in the quark sector for a specific ansatz of the 4 × 4 down-type quark mass matrix where the weak phase is generated minimally. vertex will modify in presence of the extra vector-like down-type quark. From the experimental lower bound of the partial decay width , we find the lower bound of the additional down-type quark mass. Tree level flavour changing neutral current appears in this model due to the presence of the extra vector-like down-type quark. We give the range of values of the mass splitting in system using SM box, Z-mediating tree level and Z-mediating one loop diagrams together for both q = d, s. We find the analytical expression for Γq12 in this model from standard box, Z- and Higgs-mediated penguin diagrams for system, q = d, s. From this we numerically evaluate the decay width difference . We also find the numerical values of the CP asymmetry parameters aJ and aπ for the decays B0d → J/ψKs and B0d → π+π−, respectively. We get the lower bound of the scale V through the upper bound of the strong CP phase.

RECENT RESULTS ON B DECAYS: Rare B Decay Highlights + Belle $b \to s\bar{q}q$ Time-dependent CPV

Highlights on recent experimental results on rare decays from asymmetric B-factories are reported. Also, the results on time-dependent CP violation measurements for decay modes where [Formula: see text] penguin diagram dominate from Belle are reported.

Charmless decaysB→ππ,πKandKKin broken SU(3) symmetry

Charmless B decay modes $B \to \pi \pi, \pi K$ and $KK$ aresystematically investigated with and without flavor SU(3) symmetry. Independent analyses on $\pi \pi$ and $\pi K$ modes both favor a large ratio between color-suppressed tree ($C$) and tree ($T)$ diagram, which suggests that they are more likely to originate from long distance effects. The sizes of QCD penguin diagrams extracted individually from $\pi\pi$, $\pi K$ and $KK$ modes are found to follow a pattern of SU(3) breaking in agreement with the naive factorization estimates. Global fits to these modes are done under various scenarios of SU(3)relations. The results show good determinations of weak phase $\gamma$ in consistency with the Standard Model (SM), but a large electro-weak penguin $(P_{\tmop{EW}})$ relative to $T + C$ with a large relative strong phase are favored, which requires an big enhancement of color suppressed electro-weak penguin ($P_{\tmop{EW}}^C$) compatible in size but destructively interfering with $P_{\tmop{EW}}$ within the SM, or implies new physics. Possibility of sizable contributions from nonfactorizable diagrams such as $W$-exchange ($E$), annihilation($A$) and penguin-annihilation diagrams($P_A$) are investigated. The implications to the branching ratios and CP violations in $K K$modes are discussed.

CPasymmetries and branching ratios ofB→Kπin supersymmetric models

We analyze the supersymmetric contributions to the direct and mixing CP asymmetries and also to the branching ratios of the B --> K \pi decays in a model independent way. We consider both gluino and chargino exchanges and emphasize that a large gluino contribution is essential for saturating the direct and mixing CP asymmetries. We also find that combined contributions from the penguin diagrams with chargino and gluino in the loop could lead to a possible solution for the branching ratios puzzle and account for the results of R_c and R_n within b --> s \gamma constraints. When all relevant constraints are satisfied, our result indicates that supersymmetry favors lower values of R_c. Finally we study the correlations between the mixing CP asymmetry S_{K^0 \pi^0} and mixing CP asymmetries of the processes B --> \phi K and B --> \eta' K. We show that it is quite possible for gluino exchanges to accommodate the results of that observables

Supersymmetric contributions to theB→Kπbranching ratio

We analyze the supersymmetric contributions to the $B\ensuremath{\rightarrow}K\ensuremath{\pi}$ process. We show that the simultaneous contributions from the penguin diagrams with chargino and gluino in the loop could lead to a possible solution to the $B\ensuremath{\rightarrow}K\ensuremath{\pi}$ puzzle. Our result indicates that including the stringent constraint from the $b\ensuremath{\rightarrow}s\ensuremath{\gamma}$ branching ratio, the supersymmeteric models with light right-handed top-squark and large mixing between second and third generation of up and down squarks is the most preferred by the current experimental data.