We discuss a two Higgs doublet model with extra U (1) X gauge symmetry where lepton specific (type-X) structure for Yukawa interactions is realized by charge assignment of fields under the U (1) X . Extra charged leptons are introduced to cancel gauge anomaly associated with extra gauge symmetry. In addition, we introduce scalar fields as dark matter candidates to which we assign Z 2 odd parity for guaranteeing stability of them. We then analyze phenomenology of the model such as scalar potential, muon anomalous magnetic dipole moment, collider physics associated with Z boson from U (1) X , and dark matter physics. Carrying out numerical analysis we search for phenomenologically viable parameter region.

Latest CMS results on the upper limits on σ H ± BR(H ± → τ ± ν) and σ H ± BR(H + → tb) for √ s = 13 TeV at an integrated luminosity of 35.9 fb −1 are used to impose constraints on the charged Higgs H ± parameters within the Two Higgs Doublet Model (2HDM). The 2HDM is the simplest extension of Standard Model (SM) under the same gauge symmetry to contain charged Higgs and is relatively less constrained compared to Minimal Supersymmetric Standard Model (MSSM). The latest results lead to much more stringent constraints on charged Higgs parameter space in comparison to the earlier 8 TeV results. The CMS collaboration also studied the exotic bosonic decay H ± → W ± A and A → µ + µ − for the first time and put upper limits on the BR(t → H + b) for light charged Higgs. These constraints lead to exclusion of parameter space which are not excluded by the τ ν channel. For comparison the exclusion regions from flavour physics constraints are also discussed.

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The recent measurement of the W boson mass by the CDF collaboration adds an anomaly to the long-standing discrepancy in the anomalous magnetic moment of muon. Type-X in the two-Higgs-doublet model provides an attractive solution to two anomalies through a light pseudoscalar A. However, the model confronts with the exotic Higgs decays of h → AA and the lepton flavor universality data in the τ and Z decays. To save the model, we propose that the light pseudoscalar be Higgs-phobic, i.e., λ hAA = 0. Then type-X can explain the two anomalies as well as all the other theoretical and experimental constraints. Additional requirement of the cutoff scale above 10 TeV through the RGE analysis severely limits the model, such that tan [283, 338] GeV, and M H ∈ [249, 306] GeV. Due to sizable mass gaps between M A and M H,H ± from the CDF m W measurement, dominant decay modes of H and H ± are bosonic such as H → ZA and H ± → W ± A. Since B(A → τ τ ) 100%, the golden search channels at the LHC are the 4τ states associated with two gauge bosons.

We compute the top quark threshold contributions to the γ γ production at the LHC. They appear when the invariant mass of the photon pair, M γ γ just exceeds two times the mass of the top quark and induce some feature in the M γ γ distribution. We determine the magnitude of this threshold effect and characterize this feature with a simple empirical fitting function to show that it is possible to observe this effect at the LHC in future. We also explore some possible improvements that may enhance its significance.