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Register a new userPhase structure and Higgs boson mass in a Higgs-Yukawa model with a dimension-6 operator
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We investigate the impact of a $lambda_6 varphi^6$ term included in a chirally invariant lattice Higgs-Yukawa model. Such a term could emerge from BSM physics at some larger energy scale. We map out the phase structure of the Higgs-Yukawa model with positive $lambda_6$ and negative quartic self coupling of the scalar fields. To this end, we evaluate the constraint effective potential in lattice perturbation theory and also determine the magnetization of the model via numerical simulations which allow us to reach also non-perturbative values of the couplings. As a result, we find a complex phase structure with first and second order phase transitions identified through the magnetization. Further we analyze the effect of such a $varphi^6$ term on the lower Higgs boson mass bound to see, whether the standard model lower mass bound can be altered.
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We present new results of our ongoing project on the investigation of the phase structure of the Higgs-Yukawa model at small and large bare Yukawa couplings. The critical exponents of the second order bulk phase transitions of this model are determined from finite-size analyses and compared to the pure O(4)-model to test for triviality and the possibility of having a non-Gaussian fixed point. In addition, we will present a first study of Higgs boson masses and fermion correlation functions.
We present new data on our ongoing project on the investigation of the phase structure of the Higgs-Yukawa model at large bare Yukawa couplings. The data presented last year are extended in terms of statistics, the number of bare Yukawa couplings at existing, and new larger volumes. In addition, this study is extended by a finite temperature project at the physical top quark mass m_t =175 GeV and a hypothetical fourth generation top quark with a mass of m_t =700 GeV .
We consider multi-Higgs-doublet models which, for symmetry reasons, have a universal Higgs-Yukawa (HY) coupling, $g$. This is identified with the top quark $g=g_tapprox 1$. The models are concordant with the quasi-infrared fixed point, and the top quark mass is correctly predicted with a compositeness scale (Landau pole) at $M_{planck}$, with sensitivity to heavier Higgs states. The observed Higgs boson is a $bar{t}t$ composite, and a first sequential Higgs doublet, $H_b$, with $gapprox g_tapprox 1$ coupled to $bar{b}_R(t,b)_L$ is predicted at a mass $3.0 lesssim M_b lesssim 5.5$ TeV and accessible to LHC and its upgrades. This would explain the mass of the $b-$quark, and the tachyonic SM Higgs boson mass$^2$. The flavor texture problem is no longer associated with the HY couplings, but rather is determined by the inverted multi-Higgs boson mass spectrum, e.g., the lightest fermions are associated with heaviest Higgs bosons and vice versa. The theory is no less technically natural than the standard model. The discovery of $H_b$ at the LHC would confirm the general compositeness idea of Higgs bosons and anticipate additional states potentially accessible to the $100$ TeV $pp$ machine.
The phase diagram of a chirally invariant lattice Higgs-Yukawa model is explored by means of numerical simulations. The results revealing a rich phase structure are compared to analytical large Nf calculations which we performed earlier. The analytical and numerical results are in excellent agreement at large values of Nf. In the opposite case the large Nf computation still gives a good qualitative description of the phase diagram. In particular we find numerical evidence for the predicted ferrimagnetic phase at intermediate values of the Yukawa coupling constant and for the symmetric phase at strong Yukawa couplings. Emphasis is put on the finite size effects which can hide the existence of the latter symmetric phase.
We investigate the impact of the latest data on Higgs boson branching ratios on the minimal model with a Universal Extra Dimension (mUED). Combining constraints from vacuum stability requirements with these branching ratio measurements we are able to make realistic predictions for the signal strengths in this model. We use these to find a lower bound of 1.3 TeV on the size parameter $R^{-1}$ of the model at 95% confidence level, which is far more stringent than any other reliable bound obtained till now.
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