Abdesslam Arhrib

We study the constraints of the generic two-Higgs-doublet model (2HDM) type-III and the impacts of the new Yukawa couplings. For comparisons, we revisit the analysis in the 2HDM type-II. To understand the influence of all involving free parameters and to realize their correlations, we employ $\chi$-square fitting approach by including theoretical and experimental constraints, such as S, T, and U oblique parameters, the production of standard model Higgs and its decay to $\gamma\gamma$, $WW^*/ZZ^*$, $\tau^+\tau^-$, etc. The errors of analysis are taken at $68\%$, $95.5\%$, and $99.7\%$ confidence levels. Due to the new Yukawa couplings being associated with $\cos(\beta-\alpha)$ and $\sin(\beta -\alpha)$, we find that the allowed regions for $\sin\alpha$ and $\tan\beta$ in the type-III model can be broader when the dictated parameter $\chi_F$ is positive; however, for negative $\chi_F$, the limits are stricter than those in the type-II model. By using the constrained parameters, we find that the deviation from the SM in the $h\to Z\gamma$ can be of ${\cal O}(10\%)$. Additionally, we also study the top-quark flavor-changing processes induced at the tree level in the type-III model and find that when all current experimental data are considered, we get $Br(t\to c(h, H) )< 10^{-3}$ for $m_h=125.36$ and $m_H=150$ GeV and $Br(t\to cA)$ slightly exceeds $10^{-3}$ for $m_A =130$ GeV.

We investigate the implication of the recent discovery of a Higgs-like particle in the first phase of the LHC Run 1 on the Inert Higgs Doublet Model (IHDM). The determination of the Higgs couplings to SM particles and its intrinsic properties will get improved during the new LHC Run 2 starting this year. The new LHC Run 2 would also shade some light on the triple Higgs coupling. Such measurement is very important in order to establish the details of the electroweak symmetry breaking mechanism. Given the importance of the Higgs couplings both at the LHC and $e^+e^-$ Linear Collider machines, accurate theoretical predictions are required. We study the radiative corrections to the triple Higgs coupling $hhh$ and to $hZZ$, $hWW$ couplings in the context of the IHDM. By combining several theoretical and experimental constraints on parameter space, we show that extra particles might modify the triple Higgs coupling near threshold regions. Finally, we discuss the effect of these corrections on the double Higgs production signal at the $e^+e^-$ LC and show that they can be rather important.

In this letter, we investigate the case of a twin peak around the observed 125 GeV scalar resonance, using di-Higgs production processes at both LHC and $e^{+}e^{-}$ Linear Colliders. We have shown that both at LHC and Linear Collider the triple Higgs couplings play an important role to identify this scenario; and also that this scenario can be distinguishable from any Standard Model extension by extra massive particles which might modify the triple Higgs coupling. We also introduce a criterion that can be used to ruled out the twin peak scenario.

We study the correlation between the Standard Model Higgs decay $h\to \gamma \gamma$ and $h\to Z \gamma$ in the Inert Higgs Doublet Model. It is found that these two one-loop-induced decays are positively correlated, with the later channel having slightly smaller branching ratio than the former one. At the Linear Collider, we study the interplay of the off-shell extension of these two amplitudes that contributed significantly to the associated production of the Higgs boson with a photon in the process $e^+ e^- \to \gamma h$ and with an electron in the process $e^-\gamma \to e^- h$ in the $s$ and $t$ channels respectively via both $\gamma$ and $Z$ exchange for each process.

We study the phenomenology of the Standard Model (SM) Higgs sector extended by two singlet scalars. The model predicts two CP-even scalars $h_{1,2}$ which are a mixture of doublet and singlet components as well as a pure singlet scalar $S_{0}$ which is a dark matter candidate. We show that the model can satisfy the relic density and direct detection constraints as well as all the recent ATLAS and CMS measurements. We also discuss the effect of the extra Higgs bosons on the different Higgs triple couplings $h_{i}h_{j}h_{k}$, $i,j,k=1,2$. A particular attention is given to the triple self-coupling of the SM-like Higgs where we found that the one loop corrections can reach $150\%$ is some cases. We also discuss some production mechanisms for $h_{1}$ and $h_{2}$ at the LHC as well as at the future International Linear Collider. It is found that the production cross section of a pair of SM-like Higgs bosons could be much larger than the corresponding one in the SM and would reveal physics beyond the SM if observable. We also show that in this model the branching ratio of the SM-like Higgs decaying to two singlet scalars could be of the order of $20\%$, therefore the production of the SM Higgs followed by its decay to a pair of singlets would be an important source of production of singlet scalars.