We study lepton number violating decays of charged $K$, $D$, ${D}_{s}$, $B$, and ${B}_{c}$ mesons of the form ${M}^{+}$\rightarrow${}{M}^{$'${}-}{$\ell${}}^{+}{$\ell${}}^{+}$, induced by the existence of Majorana neutrinos. These processes provide information complementary to neutrinoless double nuclear beta decays, and are sensitive to neutrino masses and lepton mixing. We explore neutrino mass ranges ${m}_{N}$ from below 1~eV to several hundred GeV. We find that in many cases the branching ratios are prohibitively small, however in the intermediate range ${m}_{$\pi${}}<{m}_{N}<{m}_{{B}_{c}}$, in specific channels and for specific neutrino masses, the branching ratios can be at the reach of high luminosity experiments like those at the LHC-$b$ and future super flavor factories, and can provide bounds on the lepton mixing parameters.

We study the Two-Higgs-Doublet Model with the aligned Yukawa sector (A2HDM) in light of the observed excess measured in the muon anomalous magnetic moment. We take into account the existing theoretical and experimental constraints with up-to-date values and demonstrate that a phenomenologically interesting region of parameter space exists. With a detailed parameter scan, we show a much larger region of viable parameter space in this model beyond the limiting case Type X 2HDM as obtained before. It features the existence of light scalar states with masses 3 GeV ≲ m _H ≲ 50 GeV, or 10 GeV ≲ m _A ≲ 130 GeV, with enhanced couplings to tau leptons. The charged Higgs boson is typically heavier, with 200 GeV ≲ m _H + ^≲ 630 GeV. The surviving parameter space is forced into the CP-conserving limit by EDM constraints. Some Standard Model observables may be significantly modified, including a possible new decay mode of the SMlike Higgs boson to four taus. We comment on future measurements and direct searches for those effects at the LHC as tests of the model.

We consider the Higgs inflation in the extension of the Standard Model with two Higgs doublets coupled to gravity non-minimally. In the presence of an approximate global U(1) symmetry in the Higgs sector, both radial and angular modes of neutral Higgs bosons drive inflation where large non-Gaussianity is possible from appropriate initial conditions on the angular mode. We also discuss the case with single-field inflation for which the U(1) symmetry is broken to aZ₂subgroup. We show that inflationary constraints, perturbativity and stability conditions restrict the parameter space of the Higgs quartic couplings at low energy in both multi- and single-field cases. Focusing on the inert doublet models whereZ₂symmetry remains unbroken at low energy, we show that the extra neutral Higgs boson can be a dark matter candidate consistent with the inflationary constraints. The doublet dark matter is always heavy in multi-field inflation while it can be light due to the suppression of the co-annihilation in single-field inflation. The implication of the extra quartic couplings on the vacuum stability bound is also discussed in the light of the recent LHC limits on the Higgs mass.

We present the implications of the recent measurement of $W$ boson at CDF II on the two-Higgs-doublet model (2HDM). In the analysis, we impose theoretical bounds such as vacuum stability and perturbative unitarity, and several experimental constraints. In addition, we take into account the measurement of ${\sin }^2{\theta }_W(m_Z{)}_{\overline{\mathrm{MS}}}$ on top of the CDF $W$-boson mass to investigate how the $S$ and $T$ parameters are determined. We explore two possible scenarios depending on whether the Higgs boson observed at the LHC is the lighter or heavier of $CP$-even neutral Higgs bosons for 2HDM type I and II. Using the results, we show how the parameter space is constrained, and compare it with the one based on the PDG average of $m_W$. Furthermore, we explore phenomenological consequences of electroweak precision observables that can be affected by $m_W$ within the predictions of the 2HDM, and the reduction in parameter space expected from future measurements at the Future Circular Lepton Collider.

Motivated by recent observations of nonzero $\theta${}13 from the Daya Bay and RENO experiments, we propose a renormalizable neutrino model with A4 discrete symmetry accounting for deviations from the tri-bimaximal mixing pattern of the neutrino mixing matrix indicated by neutrino oscillation data. In the model, the light neutrino masses can be generated by radiative corrections, and we show how the light neutrino mass matrix can be diagonalized by the Pontecorvo-Maki-Nakagawa-Sakata mixing matrix whose entries are determined by the current neutrino data, including the Daya Bay result. We show that the origin of the deviations from the tri-bimaximal mixing is nondegeneracy of the neutrino Yukawa coupling constants, and unremovable CP phases in the neutrino Yukawa matrix give rise to both low energy CP violation measurable from neutrino oscillation and high energy CP violation.