Reliable values of quark and lepton masses are important for model building at a fundamental energy scale, such as the Fermi scale $M_Z\approx 91.2\mathrm{GeV}$ and the would-be GUT scale ${\Lambda }_{\mathrm{GUT}}\sim 2\times {10}^{16}\mathrm{GeV}$. Using the latest data given by the Particle Data Group, we update the running quark and charged-lepton masses at a number of interesting energy scales below and above $M_Z$. In particular, we take into account the possible new physics scale ($\mu \sim 1\mathrm{TeV}$) to be explored by the CERN LHC and the typical seesaw scales ($\mu \sim {10}^9\mathrm{GeV}$ and $\mu \sim {10}^{12}\mathrm{GeV}$) which might be relevant to the generation of neutrino masses. For illustration, the running masses of three light Majorana neutrinos are also calculated. Our up-to-date tables of running fermion masses are expected to be very useful for the study of flavor dynamics at various energy scales.

Behind the observed pattern of lepton flavor mixing is a partial or approximate μ - τ flavor symmetry—a milestone on our road to the true origin of neutrino masses and flavor structures. In this review article we first describe the features of μ - τ permutation and reflection symmetries, and then explore their various consequences on model building and neutrino phenomenology. We pay particular attention to soft μ - τ symmetry breaking, which is crucial for our deeper understanding of the fine effects of flavor mixing and CP violation.

The recent results of the ATLAS and CMS experiments indicate 116\,\,GeV$\lesssim${}MH$\lesssim${}131\,\,GeV and 115\,\,GeV$\lesssim${}MH$\lesssim${}127\,\,GeV, respectively, for the mass of the Higgs boson in the standard model (SM) at the 95%~confidence level. In particular, both experiments point to a preferred narrow mass range MH$\simeq${}(124$\cdots${}126)\,\,GeV. We examine the impact of this preliminary result of MH on the SM vacuum stability by using the two-loop renormalization-group equations, and arrive at the cutoff scale $\Lambda${}VS$\sim${}4\ifmmode\times\else\texttimes\fi{}1012\,\,GeV (for MH=125\,\,GeV, Mt=172.9\,\,GeV, and $\alpha${}s(MZ)=0.1184), where the absolute stability of the SM vacuum is lost and some kind of new physics might take effect. We update the values of running lepton and quark masses at some typical energy scales, including the ones characterized by MH, 1~TeV and $\Lambda${}VS, with the help of the two-loop renormalization-group equations. The branching ratios of some important two-body Higgs decay modes, such as H$\rightarrow${}bb\ifmmode\bar\else\textasciimacron\fi{}, H$\rightarrow${}$\tau${}+$\tau${}-, H$\rightarrow${}$\gamma${}$\gamma${}, H$\rightarrow${}W+W-, and H$\rightarrow${}ZZ, are also recalculated by inputting the values of relevant particle masses at MH.

We propose a particularly economical neutrino mass model, in which there are only two right-handed Majorana neutrinos of $\mathcal{O}(1)$ TeV and their masses are highly degenerate. Its novel Yukawa-coupling texture together with the seesaw mechanism allows us to achieve the normal neutrino mass hierarchy with $m_1=0$ and a nearly tri-bimaximal neutrino mixing pattern with the maximal CP-violating phase: ${\theta }_{23}=\pi /4$, $|\delta |=\pi /2$ and ${\sin }^2{\theta }_{12}=(1-2{\tan }^2{\theta }_{13})/3$. One may also obtain the inverted neutrino mass hierarchy with $m_3=0$ and the corresponding neutrino mixing pattern with ${\theta }_{23}=\pi /4$ and ${\theta }_{13}=\delta =0$. In both cases, it is possible to interpret the cosmological baryon number asymmetry ${\eta }_{\mathrm{B}}\approx 6.1\times {10}^{\mathrm{-10}}$ through the resonant leptogenesis mechanism. We demonstrate the significance of flavor-dependent effects in this leptogenesis scenario: they can either flip the sign of the flavor-independent prediction for ${\eta }_{\mathrm{B}}$ in the $m_1=0$ case or magnify the magnitude of the flavor-independent prediction for ${\eta }_{\mathrm{B}}$ about 50 times in the $m_3=0$ case.