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arXiv 0705.3079hep-ph
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无粲B衰变为标量介子和矢量介子

Charmless B decays to a scalar meson and a vector meson

Hai-Yang Cheng, Chun-Khiang Chua, Kwei-Chou Yang

摘要:

在QCD因子分解的框架下研究了强子无粲B衰变为标量介子和矢量介子的过程。主要结果是:(1)$f_0(980)K^{*-}$和$f_0(980)\ov K^{*0}$模的衰减速率依赖于$f_0-σ$混合角$θ$。实验测量结果可用于$θ\approx 20^\circ$。(ii)如果$a_0(980)$是$q\bar q$束缚态,则通道$a_0^+ρ^-$和$a_0^0ρ^-$的预测分支比将非常大,分别为$30\times 10^{-6}$和$23\times 10^{-6}$阶。如果对这两种模式的观测或实验极限比$\sim 25\times 10^{-6}$的预期小得多,这可能暗示$a_0(980)$的四夸克性质。(iii)对于$a_0(1450)$通道,发现$a_0^+(1450)ρ^-$和$a_0^0(1450)ρ^-$分别具有$16\times 10^{-6}$和$22\times 10^{-6}$阶的分支比。在预测水平上测量它们将有利于$a_0(1450)$的$q\bar q$结构。(iv)与$Γ(B^-\to a_0^0ρ^-)\sim {1\over 2}Γ(\bar B^0\to a_0^+ρ^-)$的天真期望相反,我们发现它们具有可比的速率,这是由于$a_0^0$发射对$a_0ρ^-$模式的额外贡献。(v)预测的$Br(\bar B^0\to\ov K^{*0}_0(1430)ϕ)$中心值大于实验值,但在理论误差范围内。衰变$B\to K^{*}_0(1430)ρ$的速率预计将大大大于$B\to K^{*}_0(1430)π$的速率,这是由于前者(后者)中$a_4$和$a_6$企鹅项之间的相长(相消)干涉。因此,在实验上,重要的是检查$B\to K^{*}_0ρ$模式是否相对于相应的$K_0^*π$通道被增强。

英文摘要:

The hadronic charmless B decays into a scalar meson and a vector meson are studied within the framework of QCD factorization. The main results are: (i) The decay rates for the $f_0(980)K^{*-}$ and $f_0(980)\ov K^{*0}$ modes depend on the $f_0-σ$ mixing angle $θ$. The experimental measurements can be accommodated for $θ\approx 20^\circ$. (ii) If the $a_0(980)$ is a $q\bar q$ bound state, the predicted branching ratios for the channels $a_0^+ρ^-$ and $a_0^0ρ^-$ will be very large, of order $30\times 10^{-6}$ and $23\times 10^{-6}$, respectively. If the observation of or the experimental limit on theses two modes is much smaller than the expectation of $\sim 25\times 10^{-6}$, this could hint at a four-quark nature for the $a_0(980)$. (iii) For the $a_0(1450)$ channels, $a_0^+(1450)ρ^-$ and $a_0^0(1450)ρ^-$ are found to have branching ratios of order $16\times 10^{-6}$ and $22\times 10^{-6}$, respectively. A measurement of them at the predicted level will favor the $q\bar q$ structure for the $a_0(1450)$. (iv) Contrary to the naive expectation that $Γ(B^-\to a_0^0ρ^-)\sim {1\over 2}Γ(\bar B^0\to a_0^+ρ^-)$, we found that they have comparable rates due to additional contributions to the $a_0ρ^-$ mode from the $a_0^0$ emission. (v) The predicted central value of $Br(\bar B^0\to\ov K^{*0}_0(1430)ϕ)$ is larger than experiment, though it can be accommodated within theoretical errors. The decays $B\to K^{*}_0(1430)ρ$ are expected to have rates substantially larger than that of $B\to K^{*}_0(1430)π$ owing to the constructive (destructive) interference between the $a_4$ and $a_6$ penguin terms in the former (latter). Experimentally, it is thus important to check if the $B\to K^{*}_0ρ$ modes are enhanced relative to the corresponding $K_0^*π$ channels.

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