论文标题
两个比一个更好：魅力中的U-Spin-CP异常
Two is better than one: The U-spin-CP anomaly in charm
论文作者
论文摘要
The recent measurement of the CP-asymmetry in the decay $D \to K^+ K^-$ by LHCb, combined with $ΔA_{\text{CP}}$, evidences a sizable CP-asymmetry in $D \to π^+ π^-$ decays, which requires a dynamical enhancement of standard model higher-order contributions over tree-level ones by a factor两个。数据还暗示了U-Spin的巨大破裂，比标称标准型号大约4-5倍，是$ \ lyssim 30 \％$的魅力之一。增强了两个近似对称性的分解指向违反U型旋转和CP的模型，并消除了诸如铬磁偶极子操作员之类的风味单线贡献作为数据的解释。我们分析了符合CP-Asmorties的美味$ Z^\ Prime $型号的覆盖范围。模型具有明确的U-Spin和Isospin破裂，允许与$ d \ toπ^0π^0 $和$ d^+ \ toπ^+π^0 $衰减相关的cp-asmmetries的相关级别，符号为$ d \ to $ d \toπ^+π^+π^ - $，大约$ cp，cp-cal \ c. 10^{ - 3} $。实验和理论约束缩小了可行模型的形状：无异常模型是瘦恐惧症 - 或至少是电和muo-phobic-，其光$ z^\ prime $以下低于$ {\ cal {o}}（20）$ gev，并且可以在lhc and $和charm的低位dijets中搜索，并且可以在$ nc和charm的范围内搜索。 A $Z^\prime$ around $\sim 3$ GeV or $\sim (5-7)$ GeV can relieve the tensions in the $J/ψ\to π^+ π^-$ and $ψ^\prime \to π^+ π^-$ branching ratios with pion form factors from fits to Babar and JLab data, and simultaneously explain the charm CP asymmetries.模型还将相当大的分支比率带入光右中微子或类似矢量的深色费米子中，可以在Belle II和Besiii的$ E^ + E^ - \ to $ e^ + e^ - \ to $ 〜HADRONS + Invisibles中搜索。由于新的物理规模较低，深色费米子可能会引起早期的兰道杆，该杆需要在TEV规模附近进行紫外线完成。
The recent measurement of the CP-asymmetry in the decay $D \to K^+ K^-$ by LHCb, combined with $ΔA_{\text{CP}}$, evidences a sizable CP-asymmetry in $D \to π^+ π^-$ decays, which requires a dynamical enhancement of standard model higher-order contributions over tree-level ones by a factor of two. The data furthermore imply huge U-spin breaking, about 4-5 times larger than the nominal standard model one of $\lesssim 30 \%$ in charm. Enhanced breakdown of the two approximate symmetries points to models that violate U-spin and CP and disfavors flavor singlet contributions such as chromomagnetic dipole operators as explanations of the data. We analyze the reach of flavorful $Z^\prime$ models for charm CP-asymmetries. Models feature explicit U-spin and isospin breaking, allowing for correlations with $D \to π^0 π^0$ and $D^+ \to π^+ π^0$ decays with corresponding CP-asymmetries at a similar level and sign as $D \to π^+ π^-$, about $ {\cal{O}}(1-2) \cdot 10^{-3}$. Experimental and theoretical constraints narrow down the shape of viable models: anomaly-free models are leptophobic -- or at least electro- and muo-phobic -- with light $Z^\prime$ below ${\cal{O}}(20)$ GeV, and can be searched for in low mass dijets at the LHC, $Υ$ and charmonium decays, and dark photon signatures. A $Z^\prime$ around $\sim 3$ GeV or $\sim (5-7)$ GeV can relieve the tensions in the $J/ψ\to π^+ π^-$ and $ψ^\prime \to π^+ π^-$ branching ratios with pion form factors from fits to Babar and JLab data, and simultaneously explain the charm CP asymmetries. Models also feature sizable branching ratios into light right-handed neutrinos or vector-like dark fermions, which can be searched for in $e^+ e^- \to$~hadrons + invisibles at Belle II and BESIII. Due to the low new physics scale dark fermions may induce an early Landau pole which requires UV-completion near the TeV-scale.
