论文标题
CKM单位性违规，Higgs信号强度的过量和底部夸克向前不对称的矢量夸克解释
Vector-like Quark Interpretation for the CKM Unitarity Violation, Excess in Higgs Signal Strength, and Bottom Quark Forward-Backward Asymmetry
论文作者
论文摘要
由于最近对$ v_ {ud} $和$ v_ {us} $进行了更精确的评估，这是Cabbibbo-kobayashi-Maskawa（ckm）矩阵中第一行的单位条件：$ | v_ {ud | v_ {ud} |与Unity的偏差超过$4σ$。此外，总体HIGGS信号强度的轻度过度出现在标准模型（SM）预测高于2σ$上，以及向前偏远的不对称$ {\ cal a} _ {\ rm fb}^b $ in $ z \ \ b \ bar b $中的长期差异。从上述三个异常中，我们研究了SM的扩展，该SM的扩展是使用与Quark Sector相关的矢量样夸克（VLQ）的扩展，目的是减轻这些数据集中的紧张局势。我们在CKM矩阵的第一行的约束条件下执行该模型的全局拟合，$ z $ - pole observables $ {\ cal a} _ {\ rm fb}^b $，$ r_b $，$ r_b $和$γ__{观察力$ b_d^0 $ - $ \叠加{b} _d^0 $混合，$ b^+ \toπ^+ \ ell^+ \ el^+ \ el^ - $ and $ b^0 \toμ^+μ^ - $，并直接搜索大型Hadron Collider（LHC）的VLQ。我们的结果表明，将VLQ添加到SM中比SM提供更好的一致性。
Due to a recent more precise evaluation of $V_{ud}$ and $V_{us}$, the unitarity condition of the first row in the Cabibbo-Kobayashi-Maskawa (CKM) matrix: $|V_{ud}|^2 + |V_{us}|^2 + |V_{ub}|^2 = 0.99798 \pm 0.00038$ now stands at a deviation more than $4σ$ from unity. Furthermore, a mild excess in the overall Higgs signal strength appears at about $2σ$ above the standard model (SM) prediction, as well as the long-lasting discrepancy in the forward-backward asymmetry ${\cal A}_{\rm FB}^b$ in $Z\to b\bar b$ at LEP. Motivated from the above three anomalies we investigate an extension of the SM with vector-like quarks (VLQs) associated with the down-quark sector, with the goal of alleviating the tension among these datasets. We perform global fits of the model under the constraints coming from the unitarity condition of the first row of the CKM matrix, the $Z$-pole observables ${\cal A}_{\rm FB}^b$, $R_b$ and $Γ_{\rm had}$, Electro-Weak precision observables $ΔS$ and $ΔT$, $B$-meson observables $B_d^0$-$\overline{B}_d^0$ mixing, $B^+ \to π^+ \ell^+ \ell^-$ and $B^0 \to μ^+ μ^-$, and direct searches for VLQs at the Large Hadron Collider (LHC). Our results suggest that adding VLQs to the SM provides better agreement than the SM.
