Hadronic Penguin Research Articles

First evidence of new physics in [formula omitted] mixing and its implications

We present an update of the analysis of B s mixing by the UTfit Collaboration, including the very recent tagged analyses of B s → J / Ψ ϕ by the CDF and DO collaborations. We find that the phase of the B s mixing amplitude deviates more than 2.9σ from the Standard Model prediction. This results points to extensions of the Standard Model with new sources of CP violation. We compare this result with the analysis of B d mixing and show that present data favour the presence of a new source of flavour violation. Finally, we consider the impact of this analysis for SUSY models and the possible implications for new physics effects in b → s hadronic penguin decays.

Searching for New Physics inb→sHadronic Penguin Decays

We review the theoretical status of b → s hadronic penguin decays in the Standard Model and beyond. We summarize the main theoretical tools to compute branching ratios and CP asymmetries for b → s penguin-dominated nonleptonic decays and discuss the theoretical uncertainties in the prediction of time-dependent CP asymmetries in these processes. We consider general aspects of b → s transitions beyond the Standard Model. Then we present detailed predictions in supersymmetric models with new sources of flavor and CP violation.

Exploring CP violation and penguin effects through B0 d→D+D- and B0 s→D+ sD- s

The decay B0 d→D+D- offers an interesting probe of CP violation, but it requires control of penguin effects, which can be done through B0 s→D+ sD- s by means of the U-spin flavour symmetry of strong interactions. Recently, the Belle collaboration reported indications of large CP violation in the B0 d decay, which were, however, not confirmed by BaBar, and first signals of the B0 s channel were observed at the Tevatron. In view of these developments and the quickly approaching start of the LHC, we explore the allowed region in observable space for CP violation in B0 d→D+D-, perform theoretical estimates of the relevant hadronic penguin parameters and observables, and we address questions both about the most promising strategies for the extraction of CP-violating phases and about the interplay with other measurements of CP violation and the search for new physics. As far as the latter aspect is concerned, we point out that the B0 q→Dq +D- q system provides a setting for the determination of the B0 q–B0 q mixing phases (q∈{d,s}) that is complementary to the conventional B0 d→J/ψKS and B0 s→J/ψφ modes with respect to possible new-physics effects in the electroweak penguin sector.

ExploringCPviolation through correlations inB→πK,Bd→π+π−,Bs→K+K−observable space

We investigate allowed regions in observable space of B --> pi K, B_d --> pi^+pi^- and B_s --> K^+K^- decays, characterizing these modes in the Standard Model. After a discussion of a new kind of contour plots for the $B\to\pi K$ system, we focus on the mixing- induced and direct CP asymmetries of the decays B_d --> pi^+pi^- and B_s--> K^+K^-. Using experimental information on the CP-averaged B_d --> pi^{+/-}K^{+/-} and B_d --> pi^+pi^- branching ratios, the relevant hadronic penguin parameters can be constrained,implying certain allowed regions in observable space. In the case of B_d --> pi^+pi^-, an interesting situation arises now in view of the recent B-factory measurements of CP violation in this channel, allowing us to obtain new constraints on the CKM angle gamma as a function of the B^0_d--\bar{B^0_d} mixing phase phi_d=2beta, which is fixed through A_{CP}^{mix}(B_d --> J/psi K_S) up to a twofold ambiguity. If we assume that A_{CP}^{mix}(B_d --> pi^+pi^-) is positive, as indicated by recent Belle data, and that phi_d is in agreement with the ``indirect'' fits of the unitarity triangle, also the corresponding values for gamma around 60 degrees can be accommodated. On the other hand, for the second solution of phi_d, we obtain a gap around gamma ~ 60 degrees. The allowed region in the space of A_{CP}^{mix}(B_s --> K^+K^-) and A_{CP}^{dir}(B_s --> K^+K^-) is very constrained in the Standard Model, thereby providing a narrow target range for run II of the Tevatron and the experiments of the LHC era.

What is new at CLEO

I will present results from CLEO on rare B decays, particularly those arising from hadronic penguin processes, a glueball candidate f J (2220), and the hadronic cross section of the e + e − collision at the center-of-mass range around 10 GeV.

Measuring the CP angle β in hadronic b → s penguin decays

Asymmetric e^+e^- colliders running on the \Upsilon(4S) (B factories) will much more readily measure CP-violating asymmetries in the decays of B_d^0 and B^\pm mesons than in the decays of B_s^0 mesons. As such, they will seemingly not be able to probe new phases in Bs-Bs(bar) mixing, i.e. in b\to s transitions. However, by measuring the CP angle \beta via b \to s hadronic penguin decays such as B_d^0 \to \eta'\ks and B_d^0 \to\phi\ks, and comparing its value to that obtained in B_d^0 \to\Psi\ks, it is possible to detect the presence of new physics in the b\to s flavour-changing neutral current. Recent CLEO results are encouraging in this regard. They suggest that the branching ratio of the b\to s penguin decay B_d^0 \to \eta'\ks is anomalously large, about 4 \times 10^{-5}, which will make it much easier to search for new physics in b\to s transitions.

Search for rare hadronic B decays

A search for rare decays of B hadrons has been performed using approximately two million hadronic Z 0 decays collected by the OPAL experiment between 1990 and 1993. The exclusive decay channels B d 0 → π + π −, B d 0 → K +π −, B s 0 → π +K − and B s 0 → K +K − have been studied. Such decays include contributions from flavour changing neutral current processes such as hadronic penguin decays. No significant excess of events has been observed in the π +π −, π +K − and K +K − invariant mass distributions. Consequently, upper limits on the B d 0 branching ratios, Br(B d 0→ π + π −) < 4.7 × 10 −5 and Br(B d 0→K + π −) < 8.1 × 10 −5, and on the B s 0 branching ratios, Br(B s 0→ π +K −) < 2.6 × 10 −4 and Br(B s 0→K +K −) < 1.4 × 10 −4, have been set at the 90% confidence level. These limits assume that the ratio of the partial decay widths of the Z 0, λ (Z 0 → bb̄)/λ(Z 0 → hadrons), is 0.217 and that the fractions of B d 0 and B s 0 mesons produced during fragmentation are 39.5% and 12% respectively. The B s 0 branching ratio limits are the first such limits obtained.

Hadronic penguin B decays in the standard and the two-Higgs-doublet models

We study in next-to-leading order QCD hadronic penguin B decays in the Standard and two-Higgs-doublet models. Although the gluonic penguin dominates, we find the electroweak contribution non-negligible. In the Standard Model, the branching ratio for B → X s φ is predicted to be in the range (0.6–2) × 10 −4. The ranges of branching ratios for B → Kφ B → K ∗φ , and B s → φφ are (0.4−2) × 10 −5, (0.2−1) × 10 −5, and (0.15−0.5) × 10 −5, respectively. The contribution from the charged Higgs boson in two Higgs doublet models depend on cot β, and can be as large as 40%.