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Register a new userRevisiting wrong sign Yukawa coupling of type II two-Higgs-doublet model in light of the recent LHC data
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Xiao-Fang Han
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In light of the recent LHC Higgs data, we examine the parameter space of type II two-Higgs-doublet model in which the 125 GeV Higgs has the wrong sign Yukawa couplings. Combining related theoretical and experimental limits, we find that the LHC Higgs data exclude most of the parameter space of the wrong sign Yukawa coupling. For $m_H=$ 600 GeV, the allowed samples are mainly distributed in several corners and narrow bands of m_A<20 GeV, 30 GeV<m_A<120 GeV, 240 GeV<m_A<300 GeV, 380 GeV <m_A<430 GeV, and 480 GeV<m_A<550 GeV. For m_A=600 GeV, m_H is required to be less than 470 GeV. The light pseudo-scalar with a mass of 20 GeV is still allowed in case of the wrong sign Yukawa coupling of 125 GeV Higgs.
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We consider two Higgs doublet models with a softly broken U(1) symmetry, for various limiting values of the scalar mixing angles $alpha$ and $beta$. These correspond to the Standard Model Higgs particle being the lighter CP-even scalar (alignment) or the heavier CP-even scalar (reverse alignment), and also the limit in which some of the Yukawa couplings of this particle are of the opposite sign from the vector boson couplings (wrong sign). In these limits we impose a criterion for naturalness by demanding that quadratic divergences cancel at one loop. We plot the allowed masses of the remaining physical scalars based on naturalness, stability, perturbative unitarity and constraints coming from the $rho$ parameter. We also calculate the $hto gammagamma$ decay rate in the wrong sign limit.
Very recently, the CMS collaboration has reported a search for the production for a Standard Model (SM) Higgs boson in association with a top quark pair ($t bar{t} H$) at the LHC Run-2 and a best fit $t bar{t} H$ yield of $1.5 pm 0.5$ times the SM prediction with an observed significance of $3.3 sigma$. We study a possibility of whether or not this observed deviation can be explained by anomalous Higgs Yukawa couplings with the top and the bottom quarks, along with the LHC Run-1 data for the Higgs boson properties. We find that anomalous top and bottom Yukawa couplings with about $0-20$% and $10-40$% reductions from their SM values, respectively, can simultaneously fit the recent CMS result and the LHC Run-1 data.
To explain the observed muon anomaly and simultaneously evade bounds from lepton flavor violation in the same model parameter space is a long cherished dream. In view of a generalized Two Higgs Doublet Model, with a Yukawa structure as a perturbation of Type-X, we are able to get substantial parameter space satisfying this criteria. We are focusing on a region with {bf wrong-sign} lepton-Yukawa coupling which gives rise to an interesting phenomenological consequences. We found that in the wrong-sign region, it is possible to probe the low-mass pseudoscalar in flavor-violating decay mode with considerably better significance compared to the right-sign region. Performing a simple cut-based analysis we show that at 14 TeV run of the LHC with $300 fb^{-1}$ integrated luminosity, part of the model parameter space can be probed with significance $geq 5sigma$ which further improves with Artificial Neural Network analysis.
One of the main motivations to look beyond the SM is the discrepancy between the theoretical prediction and observation of anomalous magnetic moment of muon. Alleviating this tension between theory and experiment and satisfying the bounds from lepton flavor violation data simultaneously is a challenging task. In this paper, we consider generalised Two Higgs Doublet Model, with a Yukawa structure as a perturbation of Type X Two Higgs Doublet Model. In view of this model, we explore muon anomaly and lepton flavor violation along with constraints coming from B-physics, theoretical constraints, electroweak observables and collider data which can restrict the model parameter space significantly. We find that within the framework of this model it is possible to obtain regions allowed by all constraints, that can provide an explanation for the observed muon anomaly and at the same time predicts interesting signatures of lepton flavor violation. Furthermore, we consider the flavor violating decay of low-mass CP-odd scalar to probe the allowed parameter space at future runs of the LHC. With simple cut-based analysis we show that part of that parameter space can be probed with significance $> 5 sigma$. We also provide Artificial Neural Network analysis which definitely improves our cut-based results significantly.
The recent Fermilab measurement of the muon anomalous magnetic moment yields $4.2 sigma$ deviation from the SM prediction, when combined with the BNL E821 experiment results. In the Type-X two Higgs doublet model with the Higgs alignment, we study the consequence of imposing the observed muon $g-2$, along with theoretical stabilities, electroweak oblique parameters, Higgs precision data, and direct searches. For a comprehensive study, we scan the whole parameter space in two scenarios, the normal scenario where $h_{rm SM} = h$ and the inverted scenario where $h_{rm SM}=H$, where $h$ ($H$) is the light (heavy) CP-even Higgs boson. It is found that large $tanbeta$ ($gtrsim 100$) and light pseudoscalar mass $M_A$ are required to explain the muon $g-2$ anomaly. This, in turns, implies that it is difficult to maintain the theoretical stability unless the scalar masses satisfy $M_A^2 simeq M_{H^pm}^2 simeq m_{12}^2 tanbeta approx M_{H/h}^2$. The direct search bounds at the LEP and LHC exclude the small $M_A$ window below $m_{h_{rm SM}}/2$. We also show that the observed electron anomalous magnetic moment is consistent with the model prediction but the lepton flavor universality data in the $tau$ and $Z$ decays are not. For a separate exploration of the model, we propose the golden mode $pp to A h/AH to 4 tau$ at the HL-LHC, which has a high potential to probe the whole surviving parameter space.
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