Implications of Recent Measurements of Hadronic Charmless B Decays

Abstract

Implications of recent CLEO measurements of hadronic charmless B decays are discussed. (i) Employing the Bauer-Stech-Wirbel (BSW) model for form factors as a benchmark, the $B\toπ^+π^-$ data indicate that the form factor $F_0^{Bπ}(0)$ is smaller than that predicted by the BSW model, whereas the data of $B\toωπ, K^*η$ imply that the form factors $A_0^{Bω}(0), A_0^{BK^*}(0)$ are greater than the BSW model's values. (ii) The tree-dominated modes $B\toπ^+π^-, ρ^0π^\pm, ωπ^\pm$ imply that the effective number of colors N_c(LL) for (V-A)(V-A) operators is preferred to be smaller, while the current limit on $B\toϕK$ shows that N_c(LR)>3. The data of $B\to Kη'$ and $K^*η$ clearly indicate that $N_c(LR)\gg N_c(LL)$. (iii) In order to understand the observed suppression of $π^+π^-$ and non-suppression of $Kπ$ modes, both being governed by the form factor $F_0^{Bπ}$, the unitarity angle $γ$ is preferred to be greater than $90^\circ$. By contrast, the new measurement of $B^\pm\toρ^0π^\pm$ no longer strongly favors $\cosγ<0$. (iv) The observed pattern $K^-π^+\sim \ov K^0π^-\sim {2\over 3}K^-π^0$ is consistent with the theoretical expectation: The constructive interference between electroweak and QCD penguin diagrams in the $K^-π^0$ mode explains why ${\cal B}(B^-\to K^-π^0)>{1\over 2}{\cal B}(\ov B^0\to K^-π^+)$. (v) The observation $\nc(LL)<3<\nc(LR)$ and our preference for $\nc(LL)\sim 2$ and $\nc(LR)\sim 6$ are justified by a recent perturbative QCD calculation of hadronic rare B decays in the heavy quark limit.