We propose a novel solution to the Strong CP problem -- to explain why SU(3) strong force has a nearly zero theta angle $\barθ_3 \simeq 0$ for the 4d Standard Model (SM). The new ingredient is Symmetric Mass Generation (SMG): symmetry-preserving mass or energy gap can be generated without breaking any symmetry $G$ and without any quadratic mean-field mass deformation as long as $G$ is all perturbative local and nonperturbative global anomaly-free. In our first model, we propose a disordered non-mean-field SMG gap (instead of the ordered Anderson-Higgs induced mass gap) for the $u$ quark (or generally a set of quarks and leptons totally anomaly-free in $G$) generated by multi-fermion interactions or by dynamical disordered mass fields, absorbing $\barθ_3$. Another variant of this first model is the SMG gapping a hypothetical hidden full fourth family of SM fermions. In our second model, we have a chiral SM and mirror SM together to respect the Nielsen-Ninomiya fermion-doubling and a parity-reflection $\mathbb{Z}_2^{\rm PR}$ symmetry at high energy, so the $\barθ_3 = 0$. Then the SMG lifts only the mirror SM with a large energy gap but leaves the chiral SM at lower energy, which not only "spontaneously" breaks the parity-reflection symmetry maximally but also relates our solution to solve another nonperturbative chiral fermion regularization problem by removing the fermion doubling. The predictive signature of both SMG-based models is that some SM fermions or mirror fermions are highly interacting (beyond the conventional SM Higgs or SM gauge interactions) mediated through hypothetical direct multi-fermion or disordered mass-field interactions.
Constraining the charged Higgs mass in the left--right symmetric model from $b \to s γ$
在左右对称模型中，衰变$b \rightarrow s γ$主要通过$W_L$，通过$W_L$- $W_R$混合，接受规范相互作用的贡献，也接受带电标量和中性标量的汤川相互作用的贡献（后一种类型的汤川相互作用在以前的文献中被忽略了）。随着CLEO最近对包含$b \rightarrow s γ$过程的测量以及CDF和D 0合作对顶夸克质量的测量，左右对称模型的参数空间比以前更加压缩.
