从一个受GUT启发的模型解释ttbar的前后不对称性
Explaining the ttbar Forward-Backward Asymmetry from a GUT-Inspired Model
摘要：
为了解释CDF和D $Ø$报告的$t\bar{t}$前后不对称性$A^{t\bar{t}}_{FB}$，我们考虑一个模型，该模型包括来自SU（5）的{ \bf 45}和{\bf 50}表示的浅色标量。这些轻标量在标准模型规范群下用它们的电荷来标记，即来自{ \bf 50}的$(6,1)_{4/3}$和$(\bar{6},3)_{1/3}$以及来自{ \bf 45}的$(8,2)_{1/2}$。当{ \bf 50}的Yukawa耦合被合理选择并且{ \bf 45}的Yukawa耦合在$M_Z$的尺度上保持可忽略时，该模型产生与CDF在0.7 $σ$水平上报告的总$A^{t\bar{t}}_{FB}$以及与$A^{t\bar{t}}_{FB} (M_{t\bar{t}} \ge 450 \text{GeV})$在2.2 $σ$水平上报告的总$A^{t\bar{t}}_{FB}$一致的现象学上可行的结果。此外，{ \bf 50}的汤川耦合对GUT标度（其定义了在$M_Z$处的“合理选择”值）保持微扰，并且来自{ \bf 45}的光标量的存在允许在$M_{GUT} \sim 10^{17}$ GeV标度处的规范耦合统一。
英文摘要：
We consider a model that includes light colored scalars from the {\bf 45} and {\bf 50} representations of SU(5) in order to explain the CDF- and D$Ø$-reported $t\bar{t}$ forward-backward asymmetry, $A^{t\bar{t}}_{FB}$. These light scalars are, labeled by their charges under the Standard Model gauge groups, the $(6,1)_{4/3}$ and $(\bar{6},3)_{1/3}$ from the {\bf 50} and the $(8,2)_{1/2}$ from the {\bf 45}. When the Yukawa coupling of the {\bf 50} is reasonably chosen and that of the {\bf 45} kept negligible at the scale of $M_Z$, the model yields phenomenologically viable results in agreement with the total $A^{t\bar{t}}_{FB}$ reported by CDF at the 0.7$σ$ level and with $A^{t\bar{t}}_{FB} (M_{t\bar{t}} \ge 450 \text{GeV})$ at the 2.2$σ$ level. Additionally, the Yukawa coupling of the {\bf 50} remains perturbative to the GUT scale (which defines a "reasonably chosen" value at $M_Z$), and the presence of the light scalar from the {\bf 45} allows for gauge coupling unification at a scale of $M_{GUT} \sim 10^{17}$ GeV.
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