b Physics Beyond the Standard Model

I review the signals for New Physics in CP-violating measurements in B and Lambda_b decays. I also discuss ways of identifying this New Physics, should such a signal be found.Comment: 10 pages, LaTeX, 1 figure, ps file included. References adde

Precision Tests of Flavor and CP violation in B Decays

Isospin and flavor SU(3) set stringent bounds on penguin pollution in $B^0(t)\to \rho^+\rho^-$, providing a theoretically precise determination of $\alpha\equiv \phi_2$, $\alpha = (91\pm 7_{\rm exp}\pm 3_{\rm th})^\circ$. Isospin breaking in a sum rule for $B\to K\pi$ rates is shown to be suppressed. A similar sum rule holds for CP asymmetries in $B\to K\pi$. Violation of these sum rules would be evidence for an anomalous $\Delta I=1$ piece in ${\cal H}_{\rm eff}$.Comment: Reference added; Invited talk presented at the First Workshop on Theory, Phenomenology and Experiments in Heavy Flavor Physics, Anacapri, Italy, 29-31 200

Studying New Physics Amplitudes in Charmless B_s Decays

A method based on flavour SU(3) is proposed for identifying and extracting New Physics (NP) amplitudes in charmless $\Delta S=1$ $B_s$ decays using time-dependent CP asymmetries in these decays and in flavour SU(3) related $\Delta S=0$ decays. For illustration, we assume a hierarchy, $\sim 1: \lambda : \lambda^2$ ($\lambda=0.2$), between a dominant $\Delta S=1$ penguin amplitude, a NP amplitude and a Standard Model amplitude with weak phase $\gamma$. An uncertainty from SU(3) breaking corrections, reduced by using ratios of hadronic amplitudes, is further suppressed by a factor $\lambda$. We discuss examples for pairs of decays into two neutral vector mesons, $B_s\to\phi\phi, B_s\to\phi \bar K^{*0}$ and $B_s\to K^{*0}\bar K^{*0}, B^0\to K^{*0}\bar K^{*0}$, where the magnitude of the NP amplitude, its weak and strong phases can be determined.Comment: typo corrected, reference added, submitted to Physics Letters

Interpreting the time-dependent CP asymmetry in B0→π0KSB^0 \to \pi^0 K_S

Flavor SU(3) is used for studying the time-dependent CP asymmetry in $B^0 \to \pi^0 K_S$ by relating this process to $B^0\to \pi^0\pi^0$ and $B^0 \to K^+K^-$. We calculate correlated bounds on $S_{\pi K} - \sin 2\beta$ and $C_{\pi K}$, with maximal magnitudes of 0.2 and 0.3, where $S_{\pi K}$ and $C_{\pi K}$ are coefficients of $\sin\Delta mt$ and $\cos\Delta mt$ in the asymmetry. Stronger upper limits on $B^0 \to K^+K^-$ are expected to reduce these bounds and to imply nonzero lower limits on these observables. The asymmetry is studied as a function of a strong phase and the weak phase $\gamma$.Comment: 11 pages, 2 figures, to be published in Phys. Lett. B. Some equations corrected leading to small changes in figure

CP violation in B meson decays

Recent CP asymmetry measurements in tree-dominated processes, $B^0\to \pi^+\pi^-, \rho^+\rho^-, \rho^{\pm}\pi^{\mp}, B^+\to DK^+$, and in penguin-dominated decays, $B \to \pi^0 K_S, \eta' K_S, \phi K_S$, are interpreted in the framework of the Kobayashi-Maskawa (KM) mechanism of CP violation. The KM phase emerges as the dominant source of CP violation in tree-dominated decays, which are beginning to constrain the unitarity triangle beyond other constraints. Improving precision of CP asymmetry measurements in penguin-dominated decays may indicate the need for new physics.Comment: Talk presented at the Sixth International Conference on Hyperons, Charm and Beauty Hadrons, IIT, Chicago, June 27--July 3 200

Improving Bounds on Penguin Pollution in B -> pi pi

In the presence of penguin contributions, the indirect CP asymmetry in B0(t) -> pi+ pi- measures sin(2\alpha + 2\theta), where 2\theta parametrizes the size of the penguin ``pollution.'' We derive a new upper bound on |2\theta|, requiring the measurement of of BR(B+ -> pi+ pi0) and an upper bound on B00 \equiv {1\over 2} [BR(B0 -> pi0 pi0) + BR(B0bar -> pi0 pi0)]. The new bound is stronger than those previously discussed in the literature. We also present a lower bound on B00. Current data may suggest that it is not very small, in which case \theta can be determined using a complete isospin analysis.Comment: 10 pages, LaTeX, 3 figures. Abstract modified slightly. Submitted to Physics Letter

Measuring the CP Angle \beta in Hadronic b\to 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.Comment: 8 pages, LaTeX, 1 figure (included

Patterns of New Physics in B Decays

We show that any new physics (NP) which affects B decays with penguin contributions can be absorbed by redefinitions of the standard-model (SM) diagrammatic amplitudes. Hence, there are no clean signals of NP in such decays unless there is an accurate theoretical estimate of parameters or a justifiable approximation can be made. In all decays with penguin contributions, NP simultaneously affects pairs of diagrams. The evidence for a large C' from fits to B-> pi K data is naturally explained if NP contributes to P_EW, since NP affects the P_EW and C' diagrams as a pair. The weak phase gamma measured in B-> pi K decays will always agree with its SM value even in the presence of NP, if the NP contributes in such a way that the amplitudes retain the SM form after suitable redefinitions.Comment: 4 pages, revtex, no figures; Several changes made to highlight results obtaine

CKM Phases from CP Asymmetries

Measuring phases in the Cabibbo-Kobayashi-Maskawa matrix through CP asymmetries in B decays is a major goal of current and future experiments. Methods based on charge-conjugation and isospin symmetries involve very little theoretical uncertainties, while schemes based on flavor SU(3) involve uncertainties due to SU(3) breaking. Resolving these uncertainties requires further studies involving a dialogue between theory and experiments.Comment: minor corrections, several references added and update

Implications for CP asymmetries of improved data on B→K0π0B \to K^0 \pi^0

The decay $B^0 \to K^0 \pi^0$, dominated by a $b \to s$ penguin amplitude, holds the potential for exhibiting new physics in this amplitude. In the pure QCD penguin limit one expects \ckp = 0 and \skp = \sin 2 \beta for the coefficients of $\cos \Delta m t$ and $\sin \Delta m t$ in the time-dependent CP asymmetry. Small non-penguin contributions lead to corrections to these expressions which are calculated in terms of isospin-related $B\to K\pi$ rates and asymmetries, using information about strong phases from experiment. We study the prospects for incisive tests of the Standard Model through examination of these corrections. We update a prediction \ckp=0.15\pm 0.04, pointing out the sensitivity of a prediction \skp\approx 1 to the measured branching ratio for $B^0\to K^0\pi^0$ and to other observables.Comment: Note added, to be published in Physics Letters