Motivated by an anomaly in R(D ( * ) ) = BR(B → D ( * ) τ −ν )/BR(B → D ( * ) l −ν ) reported by BaBar, Belle and LHCb, we study R(D ( * ) ) in a general two Higgs doublet model (2HDM). Although it has been suggested that it is difficult for the 2HDM to explain the current world average for R(D ( * ) ), it would be important to clarify how large deviations from the standard model predictions for R(D ( * ) ) are possible in the 2HDM. We investigate possible corrections to R(D ( * ) ) in the 2HDM by taking into account various flavor physicsand find that it would be possible (impossible) to accommodate the 1σ region suggested by the Belle's result when we adopt a constraint BR(B − c → τ −ν ) ≤ 30 % (BR(B − c → τ −ν ) ≤ 10 %). We also study productions and decays of heavy neutral and charged Higgs bosons at the Large Hadron Collider (LHC) experiment and discuss the constraints and implications at the LHC. We show that in addition to well-studied production modes bg → tH − and gg → H/A, exotic productions of heavy Higgs bosons such as cg → bH + , t + H/A and cb → H + would be significantly large, and the search for their exotic decay modes such as H/A → tc + ct, µ ± τ ∓ and H + → cb as well as H/A → τ + τ − and H + → τ + ν would be important to probe the interesting parameter regions for R(D ( * ) ). arXiv:1708.06176v3 [hep-ph] 20 Nov 2017where c βα ≡ cos θ βα and s βα ≡ sin θ βα . Note that when c βα is small, the Yukawa interactions of h are almost equal to those of the SM Higgs boson, however, there are small flavor-violating interactions ρ ij f which are suppressed by c βα . On the other hand, the Yukawa interactions of heavy Higgs bosons (H, A, and H + ) mainly come from the ρ f couplings. Therefore, for the SM-like Higgs boson, the tree level flavor violation can be suppressed by the small mixing c βα and for the heavy Higgs bosons, it would be suppressed by their heaviness and/or the smallness of the extra flavor violation.Here we also stress that the interactions of the charged Higgs boson are simply parameterized by ρ f Yukawa couplings in the Higgs basis. In order to analyze the effects on R(D ( * ) ), we adopt the Higgs basis in our analysis because it is convenient to effectively understand how large deviation from the SM prediction on the R(D ( * ) ) is possible in the 2HDM, which is the aim of this paper. To understand the effects on R(D ( * ) ), we can consider some simple flavor violation in the Higgs basis. On the other hand, if we consider the simple flavor violation in the original basis, it may correspond to the complex flavor violation in the Higgs basis (as shown in Appendix A), and hence it induces the effects not only on R(D ( * ) ) but also on other processes, which may generate strong constraints in the model. In that sense, we expect that our approach is conservative to see the possibly large effects on R(D ( * ) ), but consistent with other constraints. Therefore, in our analysis, using the Higgs basis, we try to clarify how large deviations are possible within the framework of the 2HDM in...

Polarization measurements in $$ \overline{B}\to {D}^{\left(\ast \right)}\tau \overline{\nu} $$ B ¯ → D ∗ τ ν ¯ are useful to check consistency in new physics explanations for the R D and $$ {R}_{D^{*}} $$ R D * anomalies. In this paper, we investigate the D * and τ polarizations and focus on the new physics contributions to the fraction of a longitudinal D * polarization (F L D * ), which is recently measured by the Belle collaboration F L D * = 0.60 ± 0.09, in model-independent manner and in each single leptoquark model (R2, S1 and U1) that can naturally explain the $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ anomalies. It is found that ℬ(B c +  → τ + ν) severely restricts deviation from the Standard Model (SM) prediction of F L,SM D * = 0.46±0.04 in the leptoquark models: [0.43, 0.44], [0.42, 0.48], and [0.43, 0.47] are predicted as a range of F L D * for the R2, S1, and U1 leptoquark models, respectively, where the current data of $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ is satisfied at 1σ level. It is also shown that the τ polarization observables can much deviate from the SM predictions. The Belle II experiment, therefore, can check such correlations between $$ {R}_{D^{\left(\ast \right)}} $$ R D ∗ and the polarization observables, and discriminate among the leptoquark models.

In this paper, we study the extended Standard Model (SM) with an extra Higgs doublet and right-handed neutrinos. If the symmetry to distinguish the two Higgs doublets is not assigned, flavor changing neutral currents (FCNCs) involving the scalars are predicted even at the tree level. We investigate the constraints on the FCNCs at the one-loop level, and especially study the semileptonic B meson decays, e.g. B → D ( * ) τ ν and B → K ( * ) ll processes, where the SM predictions are more than 2σ away from the experimental results. We also consider the flavor-violating couplings involving right-handed neutrinos and discuss if the parameters to explain the excesses of the semileptonic B decays can resolve the discrepancy in the anomalous muon magnetic moment. Based on the analysis, we propose the smoking-gun signals of our model at the LHC. arXiv:1802.01732v2 [hep-ph] 1 Jun 2018The Standard Model (SM) succeeds in describing almost all of the experimental results. There is one Higgs doublet to break the electroweak (EW) symmetry, and the nonvanishing vacuum expectation value (VEV) of the Higgs field generates the masses of the gauge bosons and the fermions. We do not still understand the reasons why the EW scale is around a few hundred GeV and why the couplings between the Higgs field and the fermions are so hierarchical. The Higgs particle is, however, discovered at the LHC experiment, and the signal is consistent with the SM prediction [1,2]. Thus, we are certain that the SM describes our nature up to the EW scale.On the other hand, it would be true that the structure of the SM is so mysterious. In addition to the mystery of the origin of the Higgs potential and couplings, the structure of the gauge symmetry is also very non-trivial. The anomaly-free conditions are miraculously satisfied: it is not easy to add extra chiral fermions to the SM. In the bottom-up approach to the new physics, one possible extension is to add extra scalars, e.g. extra Higgs doublets, to avoid the inconsistency with the anomaly-free conditions. Such a simple extension opens up rich phenomenology, so that a simple extended SM with an extra Higgs doublet has been actually discussed since about 40 years ago [3][4][5][6][7][8][9][10].The extended SM, besides, has other interesting aspects, from the viewpoint of the top-down approach. If we consider the new physics that can solve the mysteries of the SM, we often find extra Higgs doublets. For instance, the supersymmetric extension predicts at least one more Higgs doublet. If we consider the extended gauge symmetry, such as SU (2) R , we find extra Higgs doublets that couple to the SM fermions in the effective lagrangian. If we assume that there are flavor symmetries at high energy, there would be many Higgs doublets that couple to the SM fermions flavor-dependently. Thus, it would be very interesting and important to study and summarize the predictions and the experimental constraints of the extended SM with extra Higgs doublets.Based on this background, we investigate not only the experimenta...

The discrepancy between the measured value and the Standard Model prediction for the muon anomalous magnetic moment is one of the important issues in the particle physics. In this paper, we consider a two Higgs doublet model (2HDM) where the extra Higgs doublet couples to muon and tau in lepton flavor violating (LFV) way and the one-loop correction involving the scalars largely contributes to the muon anomalous magnetic moment. The couplings should be sizable to explain the discrepancy, so that the extra Higgs bosons would dominantly decay into µτ LFV modes, which makes the model testable at the LHC through multilepton signatures even though they are produced via the electroweak interaction. We discuss the current status and the future prospect for the extra Higgs searches at the LHC, and demonstrate the reconstruction of the mass spectrum using the multi-lepton events. arXiv:1907.09845v1 [hep-ph] 23 Jul 2019 * There are other possible setups to explain this anomaly: a muon specific 2HDM [10], a lepton specific (Type-X) 2HDM [11-14], a aligned 2HDM [15-17] and a U (1)-symmetric 2HDM [18].

Recently, it was pointed out that the electron and muon g − 2 discrepancies can be explained simultaneously by a single flavor-violating axion-like particle (ALP). We show that the parameter regions favored by the muon g − 2 are already excluded by the muonium-antimuonium oscillation bound. In contrast, those for the electron g − 2 can be consistent with this bound when the ALP is heavier than 1.5 GeV. We propose to search for a signature of the same-sign and same-flavor lepton pairs and the forward-backward muon asymmetry to test the model at the Belle II experiment.