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

Suppression of flavor symmetry breaking in B decay sum rules

While flavor symmetries are useful for studying hadronic B decays, symmetry relations for amplitudes and decay rates are usually violated by first order symmetry breaking corrections. We point out two cases in which first order symmetry breaking is suppressed by a small ratio of amplitudes: (1) An isospin sum rule for four $B\to K\pi$ decays, where isospin breaking is shown to be negligible. (2) An SU(3) sum rule for pairs of $B\to K\pi$ and $B\to K\eta_8$, generalized to pairs of $B\to K\pi, B\to K\eta$ and $B\to K\eta'$.Comment: 11 pages, small corrections, one reference added, submitted to Physics Letters

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

CP Violation in B Decays: The Standard Model and Beyond

We review the subject of CP violation in $B$ decays in the Standard Model (SM) and beyond the SM. We describe some of the present most promising ways of testing the Cabibbo-Kobayashi-Maskawa (CKM) origin of CP violation through a determination of the three angles of the CKM matrix unitarity triangle. Other sources of CP nonconservation violate SM constraints on the unitarity triangle. We show that different models of physics beyond the SM can be distinguished by combining their effects in CP asymmetries and in rare flavor-changing $B$ decays.Comment: 19 page

The Role of Bs→KπB_s \to K \pi in Determining the Weak Phase γ\gamma

The decay rates for $B^0 \to K^+ \pi^-$, $B^+ \to K^0 \pi^+$, and the charge-conjugate processes were found to provide information on the weak phase $\gamma \equiv {\rm Arg}(V_{ub}^*)$ when the ratio $r$ of weak tree and penguin amplitudes was taken from data on $B \to \pi \pi$ or semileptonic $B \to \pi$ decays. We show here that the rates for $B_s \to K^- \pi^+$ and $\bar B_s \to K^+ \pi^-$ can provide the necessary information on $r$, and estimate the statistical accuracy of forthcoming measurements at the Fermilab Tevatron.Comment: 8 pages, LaTeX, no figures, submitted to Physics Letters B, corrections to discussion of SU(3) breaking adde

Diagnostic for new physics in B→πKB \to \pi K decays

A recent analysis of $B \to \pi K$ decays concludes that present data do not clearly indicate whether (i) the standard model (or $\Delta I=0$ new physics) is sufficient, or (ii) $\Delta I=1$ new physics is needed. We show that these two possibilities can be distinguished by whether a sum rule relating the CP asymmetries of the four $B \to \pi K$ decays is valid. If case (i) is favored, the sum rule holds, and one predicts $A_{CP}(\pi^0 K^0) = -0.15$, while in case (ii) fits to new physics involving large values of a color-suppressed tree amplitude entail $A_{CP}(\pi^0 K^0) = -0.03$. The current experimental average $A_{CP}(\pi^0 K^0) = -0.01 \pm 0.10$ must be measured a factor of at least three times more precisely in order to distinguish between the two cases.Comment: 10 pages, no figures. Submitted to Physics Letters B. Slight clarification adde

U-Spin Symmetry in Charmless B Decays

We prove a general theorem about equal CP rate differences within pairs of U-spin related charmless $B$ and $B_s$ decays. Large deviations from equalities would be evidence for new physics. Six pairs of decays into two pseudoscalar mesons are identified where such relations hold. Ratios of corresponding rate differences and certain ratios of rates measure U-spin breaking. These processes provide useful information on the weak phase $\gamma={\rm Arg} V^*_{ub}$. Applications of U-spin symmetry to other decays are discussed.Comment: A few typos corrected, to appear in Phys. Lett.

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

Weak phases γ\gamma and α\alpha from B+B^+, or B0B^0 and BsB_s decays

An improved flavor SU(3) method is presented for determining the weak angle $\gamma$ of the unitarity triangle using decay rates for $B^+\to K\pi, B^+\to K^+\bar K^0$ and $B^+\to \pi^+\eta$ (or $B^0\to K\pi$ and $B_s\to K \pi$), their CP-conjugate modes and the CP-averaged rate for $B^\pm\to\pi^\pm\pi^{0}$. Rescattering (color-suppressed) contribution in $B^+(B^0)\to K\pi$, for which an improved bound is obtained, is subtracted away. The only significant SU(3) breaking effects are accounted for in the factorization approximation of tree amplitudes. The weak angle $\alpha$ is obtained as a byproduct.Comment: 9 pages with 2 included eps figures; revised argument, taking into account the special shape of the amplitude quadrangle. An improved bound on rescattering effects is give

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