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arXiv 2101.02421hep-phhep-ex
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用SU（3）味对称研究$\mathcal{B}_1(\frac{1}{2}^+)\to \mathcal{B}_2(\frac{1}{2}^+)\ell^+\ell^-$半轻子弱重子衰变

Studying $\mathcal{B}_1(\frac{1}{2}^+)\to \mathcal{B}_2(\frac{1}{2}^+)\ell^+\ell^-$ Semi-leptonic Weak Baryon Decays with the SU(3) Flavor Symmetry

Ru-Min Wang, Yuan-Guo Xu, Chong Hua, Xiao-Dong Cheng

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17 pages
发表信息：
Phys. Rev. D 103, 013007 (2021)
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摘要：

受FCNC $b\to s\ell^+\ell^-$最近反常现象的启发，我们研究了SU（3）味对称的$B_1\to B_2\ell^+\ell^-(\ell=e,μ,τ)$半轻子弱衰变，其中$B_{1,2}$是单底反三重态$T_{b3}$、单粲反三重态$T_{c3}$或轻重子八重态$T_{8}$的自旋1/2重子.利用SU（3）不可约表示方法，我们首先得到了不同衰变之间的振幅关系，然后预测了这些衰变的相关的尚未测量的观测量。(a)通过测量$Λ^0_b\to Λ^0 μ^+μ^-$，我们计算了整个$q^2$区域和不同$q^2$仓中的$T_{b3}\to T_8 μ^+μ^-$和$T_{b3}\to T_8 τ^+τ^-$的分支比。其中许多是第一次获得。此外，由于SU（3）味对称性，所有$T_{b3}\to T_{8}\ell^+\ell^-$衰变的纵极化率和轻子前后不对称性在某些$q^2$仓中非常相似. (b)利用$B(Λ^+_c\to pμ^+μ^-)$和$B(Λ^+_c\to pe^+e^-)$的实验上限，对$B(T_{c3}\to T_{8}\ell^+\ell^-)$的上限进行了分析，找到了给出相关SU（3）味对称性参数有效界的$B(Λ^+_c\to pμ^+μ^-)$的实验上限. $B(Ξ^0_c \to Ξ^0e^+e^-)$和$B(Ξ^0_c \to Ξ^0μ^+μ^-)$的预言在单夸克跃迁占优势的贡献和W交换占优势的贡献之间是不同的。(c)对于$T_{8}\to T'_8 \ell^+\ell^-$衰变，我们利用$ B(Ξ^0\to Λ^0 e^+e^-)$和$ B(Σ^+\to pμ^+μ^-)$的两个测量结果分析了单夸克跃迁贡献和W交换贡献，并分别假设单夸克跃迁贡献占优势和W交换贡献占优势，给出了分支比的预言.

英文摘要：

Motivated by recent anomalies in FCNC $b\to s\ell^+\ell^-$, we study $B_1\to B_2\ell^+\ell^-(\ell=e,μ,τ)$ semi-leptonic weak decays with the SU(3) flavor symmetry, where $B_{1,2}$ are the spin-1/2 baryons of single bottomed anti-triplet $T_{b3}$, single charmed anti-triplet $T_{c3}$ or light baryon octet $T_{8}$. Using the SU(3) irreducible representation approach, we first obtain the amplitude relations among different decays, and then predict the relevant not-yet measured observables of these decays. (a) We calculate the branching ratios of the $T_{b3}\to T_8 μ^+μ^-$ and $T_{b3}\to T_8 τ^+τ^-$ in the whole $q^2$ region and in the different $q^2$ bins by the measurement of $Λ^0_b\to Λ^0 μ^+μ^-$. Many of them are obtained for the first time. In addition, the longitudinal polarization fractions and the leptonic forward-backward asymmetries of all $T_{b3}\to T_{8}\ell^+\ell^-$ decays are very similar to each other in certain $q^2$ bin due to the SU(3) flavor symmetry. (b) We analyze the upper limits of $B(T_{c3}\to T_{8}\ell^+\ell^-)$ by using the experimental upper limits of $B(Λ^+_c\to pμ^+μ^-)$ and $B(Λ^+_c\to pe^+e^-)$, and find the experimental upper limit of $B(Λ^+_c\to pμ^+μ^-)$ giving effective bounds on the relevant SU(3) flavor symmetry parameters. The predictions of $B(Ξ^0_c \to Ξ^0e^+e^-)$ and $B(Ξ^0_c \to Ξ^0μ^+μ^-)$ will be different between the single-quark transition dominant contributions and the W-exchange dominant ones. (c) As for $T_{8}\to T'_8 \ell^+\ell^-$ decays, we analyze the single-quark transition contributions and the W-exchange contributions by using two measurements of $ B(Ξ^0\to Λ^0 e^+e^-)$ and $ B(Σ^+\to pμ^+μ^-)$, and give the branching ratio predictions by assuming either single-quark transition dominant contributions or the W-exchange dominant ones.

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