arXiv subjects

Michael Gronau

Publications and source records attributed to Michael Gronau.

At least 109 records · Page 6Linked to original sources

arXiv2000

Electroweak penguin amplitudes and constraints on $γ$ in charmless $B\to VP$ decays

Electroweak penguin (EWP) amplitudes are studied model-independently in $B$ meson decays to charmless final states consisting of a vector meson ($V$) and a pseudoscalar meson ($P$). A set of SU(3) relations is derived between EWP contributions and tree amplitudes, in the approximation of retaining only the dominant EWP operators $Q_9$ and $Q_{10}$ . Two applications are described for constraining the weak phase $γ$, in $B^{\pm}\to ρ^{\pm} K^0$ and $B^{\pm}\to ρ^0 K^{\pm}$ (or $B^{\pm}\to K^{*\pm}π^0$ and $B^{\pm}\to K^{*0}π^{\pm}$), and in $B^0\to K^{*\pm}π^{\mp}$ and $B^{\pm}\toϕK^{\pm}$. Theoretical uncertainties are discussed.

hep-ph↗

arXiv2000

The Role of $B_s \to K π$ in Determining the Weak Phase $γ$

The decay rates for $B^0 \to K^+ π^-$, $B^+ \to K^0 π^+$, and the charge-conjugate processes were found to provide information on the weak phase $γ\equiv {\rm Arg}(V_{ub}^*)$ when the ratio $r$ of weak tree and penguin amplitudes was taken from data on $B \to ππ$ or semileptonic $B \to π$ decays. We show here that the rates for $B_s \to K^- π^+$ and $\bar B_s \to K^+ π^-$ can provide the necessary information on $r$, and estimate the statistical accuracy of forthcoming measurements at the Fermilab Tevatron.

hep-ph↗

arXiv2000

Determining the CP violating phase $γ$

We review several methods for determining the Kobayashi-Maskawa phase $γ={\rm Arg} V^*_{ub}$ from rate and CP asymmetry measurements in hadronic B decays. We focus on the processes $B\to DK, B_s\to D_s K$, and on charmless decays to two light pseudoscalars and decays to a pair of a pseudoscalar and a vector meson. Theoretical uncertainties underlying these methods are discussed.

hep-ph↗

arXiv1999

New Information on B Decays to Charmless VP Final States

The decays of $B$ mesons to charmless final states consisting of a vector meson ($V$) and a pseudoscalar meson ($P$) are analyzed within flavor SU(3). Predictions are compared with new data from the CLEO Collaboration. Dominant contributions to amplitudes and subdominant interfering terms are identified. Evidence is found for a specific penguin amplitude (contributing, for example, to $B^+ \to ρ^+ K^0$) at a level much higher than that implied by most explicit models. The validity of the conclusion $\cos γ< 0$, obtained through other analyses of $B \to VP$ decays, is examined here from a less model-dependent standpoint. It is found that several processes are consistent with $\cos γ< 0$ (or $\cos α> 0$), and measurements are suggested which could make this conclusion more robust.

hep-ph↗

arXiv1999

Resonant Two-body D Decays

The contribution of a $K^*(1430)$ $0^+$ resonance to $D^0\to K^-π^+$ is calculated by applying the soft pion theorem to $D^+ \to K^* π^+$, and is found to be about 30% of the measured amplitude and to be larger than the $ΔI=3/2$ component of this amplitude. We estimate a 70% contribution to the total amplitude from a higher $K^*(1950)$ resonance. This implies large deviations from factorization in D decay amplitudes, a lifetime difference between D^0 and D^+, and an enhancement of $D^0-\bar D^0$ mixing due to SU(3) breaking.

hep-ph↗

arXiv1999

CP Violation and B Physics

This is a quick review of CP non-conservation in $B$ physics. Several methods are described for testing the Kobayashi-Maskawa single phase origin of CP violation in B decays, pointing out some limitations due to hadronic uncertainties. A few characteristic signatures of new physics in B decay asymmetries are listed.

hep-ph↗

arXiv1999

Penguins in CP violating B decays

The role of penguin amplitudes in CP violating $B$ decays is reviewed, emphasizing recent progress in the analysis of electroweak penguin contributions. It is shown how these terms are included in a model-independent manner when measuring the weak phase $α$ in $B\toππ$ using isospin symmetry, and when determining the phase $γ$ from $B\to Kπ$ applying flavor SU(3). Uncertainties due to rescattering effects in $B\to Kπ$ are discussed.

hep-ph↗

arXiv1999

A Critical Look at Rescattering Effects on $γ$ from $B^+\to Kπ$

Three ways are compared of dealing with rescattering effects in $B^{\pm}\to K^0π^{\pm}$, in order to determine the weak phase $γ$ from these processes and $B^{\pm}\to K^{\pm}π^0$. We find that neglecting these contributions altogether may involve sizable errors in $γ$, depending on the rescattering amplitude and on the value of a certain measurable strong phase. We show that an attempt to eliminate these effects by using the charge-averaged rate of $B^{\pm}\to K^{\pm}K^0$ suffers from a large theoretical error due to SU(3) breaking, which may be resolved when using also the processes $B^{\pm}\to π^{\pm}η_8$.

hep-ph↗

arXiv1998

Weak phases $γ$ and $α$ from $B^+$, or $B^0$ and $B_s$ decays

An improved flavor SU(3) method is presented for determining the weak angle $γ$ of the unitarity triangle using decay rates for $B^+\to Kπ, B^+\to K^+\bar K^0$ and $B^+\to π^+η$ (or $B^0\to Kπ$ and $B_s\to K π$), their CP-conjugate modes and the CP-averaged rate for $B^\pm\toπ^\pmπ^{0}$. Rescattering (color-suppressed) contribution in $B^+(B^0)\to Kπ$, 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 $α$ is obtained as a byproduct.

hep-ph↗

arXiv1998

Combining CP Asymmetries in $B \to K π$ Decays

We prove an approximate relation, to leading order in dominant terms, between CP-violating rate differences in $B^0/\bar{B}^0 \to K^{\pm}π^{\mp}$ and $B^{\pm} \to K^{\pm}π^0$. We show how data from these two processes may be combined in order to enhance the significance of a nonzero result.

hep-ph↗

arXiv1998

Model-independent electroweak penguins in B decays to two pseudoscalars

We study the effects of electroweak penguin (EWP) amplitudes in $B$ meson decays into two charmless pseudoscalars in the approximation of retaining only the dominant EWP operators $Q_9$ and $Q_{10}$. Using flavor SU(3) symmetry, we derive a set of model-independent relations between EWP contributions and tree-level decay amplitudes one of which was noted recently by Neubert and Rosner. Two new applications of these relations are demonstrated in which uncertainties due to EWP corrections are eliminated in order to determine a weak phase. Whereas the weak angle $α$ can be obtained from $B\toππ$ free of hadronic uncertainties, a determination of $γ$ from $B^{0,\pm}\to Kπ^{\pm}$ requires the knowledge of a ratio of certain tree-level hadronic matrix elements. The smallness of this ratio implies a useful constraint on $γ$ if rescattering can be neglected.

hep-ph↗

arXiv1998

Rescattering Information from $B \to K \bar K$ Decays

Rescattering effects can modify the dependence on the weak phase $γ= -{\rm Arg}(V^*_{ub}V_{ud}/V^*_{cb} V_{cd})$ of the ratio of rates for $B^{\pm} \to K π^\pm$ and $B \to K^\pm π^\mp$. A test for these effects based on the processes $B^\pm \to K^\pm K$ has been suggested. It is pointed out that the rates for the processes $B \to K^+ K^-$, which are expected to be {\it dominated} by rescattering and for which considerably better experimental bounds exist, are likely to provide a more stringent constraint on these effects.

hep-ph↗

arXiv1998

Final State Interaction Effects on $γ$ from $B \to D K$

The implications of a negligible annihilation contribution in $B \to D K$ decays are reanalyzed and are shown to lead to no new constraints on the weak phase $γ$ from color-allowed $B^{\pm} \to D K^{\pm}$ decays. A test of negligible annihilation is proposed in $B^+ \to D^+ K^0$ (or $B^+ \to D^+ K^{*0}$), and an application is presented in which $γ$ can be determined from these processes (or corresponding $B \to D K^*$ decays) supplemented with isospin-related neutral $B$ decays.

hep-ph↗

arXiv1998

Weak phase $γ$ from color-allowed $B \to D K$ rates

The ratios of partial rates for charged B decays to the recently observed $D^0 K$ mode and to the two $D_{CP}K$ final states (CP = $\pm$) are shown to constrain the weak phase $γ\equiv {\rm Arg} (V_{ub}^*)$. The smaller color-suppressed rate, providing further information about the phase, can be determined from these rates alone. Present estimates suggest that, while the first constraints can already be obtained in a high luminosity e^+e^- B factory, measuring the color-suppressed rate would require dedicated hadronic B production experiments.

hep-ph↗

arXiv1998

Weak Phase $γ$ From Ratio of $B \to K π$ Rates

The ratio of partial decay rates for charged and neutral $B$ mesons to $K π$ final states provides information on the weak phase $γ\equiv {\rm Arg} (V_{ub}^*)$ when augmented with information on the CP-violating asymmetry in the $K^\pm π^\mp$ mode. The requirements for a useful determination of $γ$ are examined in the light of present information about the decays $B^0 \to K^+ π^-$, $B^+ \to K^0 π^+$, and the corresponding charge-conjugate modes. The effects of electroweak penguins and rescattering corrections are noted, and proposals are made for estimating and measuring their importance.

hep-ph↗

arXiv1997

B Decays Involving $η$ and $η'$ in the Light of the $B \to K η'$ Process

The observation by the CLEO Collaboration of the decays $B^{(+,0)} \to K^{(+,0)} η'$ is shown to imply a significant but still uncertain contribution from the flavor-SU(3)-singlet component of the $η'$. By comparing the rate for these decays with others for decays of B mesons to two pseudoscalar mesons, it is shown that the prospects for observing CP-violating asymmetries in certain modes such as $B^+ \to π^+ η$ and $B^+ \to π^+ η'$ are quite bright.

hep-ph↗

arXiv1997

B Decays to Charmless VP Final States

The CLEO Collaboration has now observed the decays $B^+ \to ωπ^+$ and $B \to ωK^+$ with branching ratios of $(1.1^{+0.6}_{-0.5} \pm 0.2) \times 10^{-5}$ and $(1.5^{+0.7}_{-0.6} \pm 0.3) \times 10^{-5}$, respectively. These are the first reported decays to charmless final states involving a vector (V) and a pseudoscalar (P) meson. The implications of these decays for others of B mesons to charmless VP final states are explored. In a model-independent approach, using only flavor SU(3) symmetry, several tests are proposed for an anticipated hierarchy among different contributions to decay amplitudes.

hep-ph↗

arXiv1997

Theory of CP Violation

CP violation in K and B decays is reviewed in the Standard Model (SM) and beyond the SM. In K decays, one is seeking first evidence for CP violation in direct $K\to ππ$ decays. This would not give a precise quantitative test for the present explanation of CP violation in terms of a phase in the Cabibbo-Kobayashi-Maskawa (CKM) matrix. Such tests are provided by a variety of CP asymmetries in neutral and charged B decays. Certain features, characterizing CP violation beyond the standard model, are outlined in the B meson system.

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