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arXiv 1905.07591hep-phhep-exhep-lat
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二重轴矢量四夸克态$T_{bc;\bar{u}\bar{d}}^{0}$

Double-heavy axial-vector tetraquark $T_{bc;\bar{u}\bar{d}}^{0}$

S. S. Agaev, K. Azizi, H. Sundu

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11 Pages, 3 Figures and 4 Tables
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摘要：

用QCD两点求和规则方法计算了轴矢量四夸克态$T_{bc;\bar{u}\bar{d} }^{0}$（简称$T_{bc}^{0}$）的质量和耦合。在计算中，我们考虑到各种夸克，胶子和混合真空凝聚到10维所产生的贡献。质量$m=(7105 \pm 155)~\mathrm{ MeV}$的中心值位于$T_{bc}^{0}$态的强衰变和电磁衰变的阈值之下，因此它只能通过弱衰变转变为常规介子。在$m=7260~\mathrm{MeV}$的情况下，四夸克$T_{bc}^{0}$成为强相互作用和电磁相互作用的不稳定粒子。在第一种情况下，我们利用$ T_{bc}^{0}$的主导半轻子衰变$T_{bc}^{0}\to T_{cc;\bar{ u}\bar{d}}^{+}l\overline{ν}_{l}$（$l=e,\ μ, τ$）计算了它的全宽和平均寿命，其中末态四夸克态是标量态。我们还计算了非轻子弱衰变$T_{bc}^{0}\to T_{cc;\bar{u}\bar{d} }^{+}π^{-}(K^{-}, D^{-}, D_{s}^{-})$的部分宽度，并考虑了它们对$T_{bc}^{0}$全宽度的影响。在第二种情况下，我们计算部分宽度的$S$波强衰变$T_{bc}^{0}\to B^{\ast -}D^{+}$和$T_{bc}^{0}\to \overline{B}^{\ast 0}D^{0}$，并使用这些通道评估$T_{bc}^{0}$的全宽。在第一种情况下得到的对$Γ_{ \mathrm{full}} =(3.98\pm 0.51)\times 10^{-10}~\mathrm{MeV}$和$T_{bc}^{0}$的平均寿命$τ=1.65_{-0.18}^{+0.25}~\mathrm{ps}$的预言，以及在第二种情况下得到的全宽$Γ_{\mathrm{ full}}=(63.5\pm 8.9)~\mathrm{MeV}$，可能对二重奇异介子的实验和理论探索是有用的。

英文摘要：

The mass and coupling of the axial-vector tetraquark $T_{bc;\bar{u}\bar{d} }^{0}$ (in a short form $T_{bc}^{0}$) are calculated by means of the QCD two-point sum rule method. In computations we take into account contributions arising from various quark, gluon and mixed vacuum condensates up to dimension 10. The central value of the mass $m=(7105 \pm 155)~\mathrm{ MeV}$ lies below the thresholds for the strong and electromagnetic decays of $T_{bc}^{0}$ state, and hence it transforms to conventional mesons only through the weak decays. In the case of $m=7260~\mathrm{MeV}$ the tetraquark $T_{bc}^{0}$ becomes the strong- and electromagnetic-interaction unstable particle. In the first case, we find the full width and mean lifetime of $ T_{bc}^{0}$ using its dominant semileptonic decays $T_{bc}^{0}\to T_{cc;\bar{ u}\bar{d}}^{+}l\overline{ν}_{l}$ ($l=e,\ μ, τ$), where the final-state tetraquark is a scalar state. We compute also partial widths of the nonleptonic weak decays $T_{bc}^{0}\to T_{cc;\bar{u}\bar{d} }^{+}π^{-}(K^{-}, D^{-}, D_{s}^{-})$, and take into account their effects on the full width of $T_{bc}^{0}$. In the context of the second scenario we calculate partial widths of $S$-wave strong decays $T_{bc}^{0}\to B^{\ast -}D^{+}$ and $T_{bc}^{0}\to \overline{B}^{\ast 0}D^{0}$, and using these channels evaluate the full width of $T_{bc}^{0}$. Predictions for $Γ_{ \mathrm{full}} =(3.98\pm 0.51)\times 10^{-10}~\mathrm{MeV}$ and mean lifetime $τ=1.65_{-0.18}^{+0.25}~\mathrm{ps}$ of $T_{bc}^{0}$ obtained in the context of the first option, as well as the full width $Γ_{\mathrm{ full}}=(63.5\pm 8.9)~\mathrm{MeV}$ extracted in the second scenario may be useful for experimental and theoretical exploration of double-heavy exotic mesons.

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