CP4 3HDM is a three-Higgs-doublet model based on the $CP$ symmetry of order 4 (CP4). Imposing CP4 leads to remarkable connections between the scalar and Yukawa sectors and unavoidably generates tree-level flavor-changing neutral couplings (FCNC). It remains unclear whether FCNC can be sufficiently suppressed in the CP4 3HDM. In this paper, we systematically explore this issue. We first develop an efficient scanning procedure which takes the quark masses and mixing as input and expresses the FCNC matrices in terms of physical quark observables and quark rotation parameters. This procedure allows us to explore the FCNC effects for all the Yukawa sectors possible within the CP4 3HDM. We find that, out of the eight possible CP4 Yukawa sectors, only two scenarios are compatible with the $K$, $B$, $B_s$ and, in particular, $D$-meson oscillation constraints. The results of this work serve as clear guidelines for future phenomenological scans of the model.
Cancellation Mechanism of FCNCs in S_4 x Z_2 Flavor Symmetric Extra U(1) Model
我们提出了一个具有非阿贝尔离散味对称性的E_6超对称模型:SU(3)_c x SU(2)_W x U(1)_Y x U(1)_X x S_4 x Z_2.在我们的方案中,附加的阿贝尔规范对称性U(1)_X不仅解决了最小超对称标准模型(MSSM)中的μ问题,而且还需要新的奇异场,这些奇异场在解决味之谜中起着重要的作用。如果我们的奇异夸克能嵌入到对应于代数的S_4三重态中,我们发现危险的质子衰变能被很好地抑制。因此,可以预期,在SM(标准模型)轻子和夸克的产生结构可以理解为一个新的系统,以稳定的质子在超对称标准模型(SUSY)。此外,由于离散的非阿贝尔对称性本身的性质,我们的模型的汤川耦合常数大大减少。在我们之前的工作中,我们实际上已经取得了很大的成功。然而,我们还必须在树的水平上解决希格斯介导的FCNC,这是这种扩展希格斯模型的常见情况。在本文中,我们提出了一个很有前途的机制,可以使之间的抵消希格斯和超对称贡献。
FCNC and CP Violation Observables in a SU(3)-flavoured MSSM
最小超对称标准模型的非阿贝尔味对称性可以解释汤川耦合的味结构,同时解决超对称味问题。类似地,如果CP在风味区段中自发地被破坏,则超对称CP问题可以被解决。在这项工作中,我们提出了一个明确的例子,这些声明与SU(3)味对称性和自发的CP破坏。此外,我们表明,它仍然是可能的,找到一些重大偏离SM的期望,就FCNC和CP破坏而言。我们发现轻子味破坏衰变如$μ\to e γ$和$τ\to μγ$、电偶极矩$d_e$和$d_n$以及K介子CP破坏过程如$ε_K$都有很大的贡献。因此,这些风味MSSM的实现是现象敏感的风味和CP vioation物理领域的实验研究。
We propose a 3+1 Higgs Doublet Model based on the $Δ(27)$ family symmetry supplemented by several auxiliary cyclic symmetries leading to viable Yukawa textures for the Standard Model fermions, consistent with the observed pattern of fermion masses and mixings. The charged fermion mass hierarchy and the quark mixing pattern is generated by the spontaneous breaking of the discrete symmetries due to flavons that act as Froggatt-Nielsen fields. The tiny neutrino masses arise from a radiative seesaw mechanism at one loop level, thanks to a preserved $Z_2^{\left( 1\right)}$ discrete symmetry, which …
A Peccei-Quinn~(PQ) symmetry is proposed in order to generate in the Standard Model~(SM) quark sector a realistic mass matrix ansatz with five texture-zeros. Limiting our analysis to Hermitian mass matrices, we show that this requires a minimum of 4 Higgs doublets. This model allows assigning values close to 1 for several Yukawa couplings, giving insight into the origin of the mass scales in the SM. Since the PQ charges are non-universal, the model features Flavor-Changing Neutral Currents~(FCNC) at the tree level. From the analytical expressions for the FCNC we report the allowed region in th…
Anomalous U(1) Gauge Symmetry and Lepton Flavor Violation
近年来,许多人研究了反常U(1)规范对称性是超对称破缺的触发器和/或费米子质量等级的起源的可能性。虽然有趣的是,反常的U(1)对称性可以同时解释这两种现象,但它会导致负的终止质量平方或严重的微调,以避免FCNC问题。最近,有人指出,F-项的贡献的介子场可以支配的味道依赖的贡献,从反常U(1)D-项,因此,FCNC问题可以自然地避免。本文研究了Kähler势变形使介子稳定的情形,发现F项与D项贡献之比的量级一般是确定的。这意味着μ \to e γ的分支比可以在当前实验界限附近找到。
SUSY induced top quark FCNC decay $t \to c h$ after Run I of LHC
鉴于希格斯玻色子的发现和在大型强子对撞机上未观测到超对称粒子,我们重新审视了超对称诱导的顶夸克味变衰变为希格斯玻色子。通过考虑Higgs质量测量、LHC对SUSY的搜索、真空稳定性、精确电弱观测量以及$B \to X_s γ$的约束,我们对相关的SUSY参数空间进行了扫描。我们得到了以下结果:(1)在MSSM中,$ t \to c h$的分支比只能达到$3.0\times10^{-6}$,这比LHC出现之前的结果小了一个数量级。在考虑的约束,希格斯质量和LHC搜索sparticles被发现发挥了重要作用,限制预测。(2)在MSSM的单重态扩展中,由于夸克扇区不受Higgs质量的限制,$t \to c h$的分支比在允许的参数空间中可以达到$10^{-5}$的量级. (3)在重超对称极限下,手性守恒的混合物$δ_{LL}$和$δ_{RR}$对$t \to c h$可能有抑制作用.在方子和胶子能量大于3TeV,CP奇Higgs玻色子质量约为1TeV的MSSM中,$t\to c h$的分支比仍能达到$10^{-8}$的量级.
我们讨论了如何,在高维算子的存在下,标准模型(SM)的费米子质量可以在味空间与汤川耦合的希格斯玻色子,即使只有一个希格斯偶线错位。这种错位导致了与希格斯粒子的变味耦合,从而导致了来自树能级希格斯交换的变味中性流(FCNC)过程。我们对这种效应进行了独立于模型的分析。专门的框架的复合希格斯粒子与部分复合SM规范和费米子场,我们表明,的约束的复合尺度隐含的PINK可以一般一样强,从交换的重自旋-1共振,如果希格斯是轻的,强耦合到新的状态。在一个特殊的和动机良好的情况下,一个复合的伪戈德斯通希格斯粒子,我们发现,移动对称性作用于希格斯粒子的部队对齐的费米子质量项与他们的汤川耦合在领先的费米子的复合度,从而意味着更温和的边界。由于味道违反的希格斯耦合,我们估计BR(t -> c h)~ 10^{-4}和BR(h -> tc)~ 5 x 10^{-3},无论是对于伪戈德斯通(如果t_R是完全复合的)还是对于一般的复合希格斯。借助于AdS/CFT对应,我们的结果直接适用于5维Randall-Sundrum紧化.
The observed flavor-changing neutral-current (FCNC) processes in the standard model (SM) arise from the loop diagrams involving the weak charged currents mediated by the $W$-gauge boson. Nevertheless, the top-quark FCNCs and lepton-flavor violating processes resulting from the same mechanism are highly suppressed. We investigate possible new physics effects that can enhance the suppressed FCNC processes, such as $t\to q(h,V)$ with $V=γ,Z,g$, $h\to \ell \ell'$, and $\ell\to \ell' γ$. To achieve the assumption that the induced-FCNCs are all from quantum loops, we consider the scotogenic mechanis…
In the framework of the Standard Model Effective Field Theory, we compare the lower bounds on the scale of new physics possibly contributing to the $f\bar{f}h$ effective couplings, obtained from the measurements of different observables, under the assumption that the Wilson coefficients of the relevant dim 6 operators respect certain flavour structure: either the Minimal Flavour Violation (MFV) ansatz or a flavour symmetry, often invoked to explain the observed pattern of fermion masses and mixings. We perform a global analysis of the bounds following from the limits on the diagonal couplings …
A three Higgs-doublet model admitting an $S_3$-symmetry can predict the observed pattern of the quark masses and their mixings. However the same symmetry also introduces potential flavour-changing neutral currents at the tree level. We assume in this work that the scalar potential contains appropriate \emph{soft} $S_3$-breaking terms in order to keep the choices of the scalar masses flexible. We identify the parameters in the Yukawa Lagrangian in the quark sector responsible for such FCNCs and constrain them using data from some of the flavour physics observables like meson-decays and meson-mi…
We analyse $Z^\prime$ contributions to FCNC processes at the one-loop level. In analogy to the CKM matrix we introduce two $3\times3$ unitary matrices $\hatΔ_d(Z^\prime)$ and $\hatΔ_u(Z^\prime)$ which are also hermitian. They govern the flavour interactions mediated by $Z^\prime$ between down-quarks and up-quarks, respectively, with $\hatΔ_d(Z^\prime)=\hatΔ_u(Z^\prime)\equiv \hatΔ_L(Z^\prime)$ for left-handed currents due to the unbroken $\text{SU(2)}_L$ gauge symmetry. This assures the suppression of these contributions to all $Z^\prime$ mediated FCNC processes at the one-loop level. As, in c…