We present the general formalism for studying CP-violating phenomena in the production, mixing and decay of a coupled system of CP-violating neutral Higgs bosons at high-energy colliders. Considering the Minimal Supersymmetric Standard Model (MSSM) Higgs sector in which CP violation is radiatively induced by phases in the soft supersymmetry-breaking third-generation trilinear squark couplings and gaugino masses, we apply our formalism to neutral Higgs production viabb, gg and W + W − collisions at the LHC. We discuss CP asymmetries in the longitudinal and transverse polarizations of τ + τ − pairs.

After the discovery of the Higgs boson at the LHC, it is natural to start the research program on the precision study of the Higgs-boson couplings to various standard model (SM) particles. We provide a generic framework for the deviations of the couplings from their SM values by introducing a number of parameters. We show that a large number of models beyond the SM can be covered, including two-Higgs-doublet models, supersymmetric models, little-Higgs models, extended Higgs sectors with singlets, and fourth generation models. We perform global fits to the most updated data from CMS, ATLAS, and Tevatron under various initial conditions of the parameter set. In particular, we have made explicit comparisons between the fitting results before and after the Moriond 2013 meetings. Highlights of the results include: (i) the nonstandard decay branching ratio of the Higgs boson is less than 22%; (ii) the most efficient way to achieve the best fit for the data before the Moriond update is to introduce additional particle contributions to the triangularloop functions of Hγγ and Hgg vertices; (iii) the 1σ allowed range of the relative coupling of HV V is 1.01 +0.13 −0.14 , which means that the electroweak-symmetry breaking contribution from the observed Higgs boson leaves only a small room for other Higgs bosons; (iv) the current data do not rule out pseudoscalar couplings nor pseudoscalar contributions to the Hγγ and Hgg vertices; and (v) the SM Higgs boson provides the best fit to all the current Higgs data.

During the 2014 Summer Conferences, both ATLAS and CMS Collaborations of the LHC experiments have demonstrated tremendous efforts in treatment of data and processing more data such that most data on signal strengths have improved; especially the diphoton and fermionic modes of both experiments. Here in this note we perform an update to our previous model-independent Higgs precision analysis -Higgcision. We found the followings: (i) the uncertainties on most couplings shrink about 10-20%, (ii) the nonstandard (e.g. invisible) decay branching ratio of the Higgs boson is constrained to be less than 19% if only the width is allowed to vary, (iii) the gauge-Higgs coupling C v is constrained to be 0.94−0.12 , in which the uncertainty is reduced by about 10%, and (iv) the standard model (SM) Higgs boson still provides the best fit to all the Higgs boson data, and compared to the previous results the SM Higgs boson now enjoys a higher p value than the last year.

Current data on the signal strengths and angular spectrum of the 125.5 GeV Higgs boson still allow a CP-mixed state, namely, the pseudoscalar coupling to the top quark can be as sizable as the scalar coupling: C S u ≈ C P u = 1/2. CP violation can then arise and manifest in sizable electric dipole moments (EDMs). In the framework of twoHiggs-doublet models, we not only update the Higgs precision (Higgcision) study on the couplings with the most updated Higgs signal strength data, but also compute all the Higgs-mediated contributions from the 125.5 GeV Higgs boson to the EDMs, and confront the allowed parameter space against the existing constraints from the EDM measurements of Thallium, neutron, Mercury, and Thorium monoxide. We found that the combined EDM constraints restrict the pseudoscalar coupling to be less than about 10 −2 , unless there are contributions from other Higgs bosons, supersymmetric particles, or other exotic particles that delicately cancel the current Higgs-mediated contributions.

We perform a model independent analysis on qq → tt using an effective lagrangian with dim-6 four-quark operators, and derive necessary conditions on new physics that are consistent with the tt production cross section and the forward-backward (FB) asymmetry (AFB) measured at the Tevatron. We also propose a new FB spin-spin correlation that is strongly correlated with the AFB, and discuss possible new physics scenarios that could generate such dim-6 operators.

arXiv:1804.07130v3 [hep-ph] 15 Jul 2019 Higgs boson are very different among the SM, two-Higgs doublet models (2HDM), and MSSM. One of the probes of Higgs self-coupling is Higgs-boson-pair production at the LHC [4][5][6]. There have been a large number of works in literature on Higgs-pair production in the SM [7], in model-independent formalism [8], in models beyond the SM [9], and in SUSY [10]. The predictions for various models are largely different such that the production rates can give valuable information on the self-coupling λ 3H . In the SM, Higgs-pair production receives contributions from both the triangle and box diagrams, which interfere with each other. It is only the triangle diagram that involves the Higgs self-trilinear coupling λ 3H , yet the top-Yukawa coupling appears in both triangle and box diagrams. Therefore, we have to disentangle the triangle diagram from the box diagram in order to probe the Higgs trilinear coupling. In Ref.[11], we pointed out that the triangle diagram, with s-channel Higgs propagator, is more important at low invariant-mass region than the box diagram. Thus, the Higgs-boson pair from the triangle diagram tends to have lower invariant mass, and therefore the opening angle in the decay products of each Higgs boson tends to be larger than that from the box diagram. Indeed, the opening angle separations ∆R γγ and ∆R bb between the decay products of the Higgs-boson pair are very useful variables to disentangle the two sources. However, in Ref. [11] we only assumed some level of signal uncertainties to evaluate the sensitivity to the parameter space of self-coupling λ 3H and the top-Yukawa coupling g S t , without calculating all the other SM backgrounds, e.g., jet-fake backgrounds, single Higgs associated backgrounds, and non-resonant backgrounds.In this work, we perform the most up-to-date comprehensive signal-background analysis for Higgs-pair production through gluon fusion and the HH → bbγγ decay channel. For other production and decay channels and some combined analyses, see Refs. [12]. We simulate the signal and all background processes using simulation tools as sophisticated as what experimentalists use. The signal subprocess is gg → HH → bbγγ with various values for λ 3H . The background includes tt, ttγ, single Higgs associated backgrounds (e.g. ZH, ttH, bbH, ggH followed by H → γγ), and non-resonant or jet-fake backgrounds (e.g. bbγγ, bbjγ, bbjj, jjγγ, etc). We found a set of useful selection cuts to reduce the backgrounds. We express the sensitivity that can be achieved in terms of significance. We find that even for the most promising channel HH → bbγγ at the HL-LHC, the significance is still not high enough to establish the Higgs self-coupling at the SM value, though the self-coupling can be constrained to the range 0 < λ 3H < 7.1 at 95% confidence level (CL) with an integrated luminosity of 3000 fb −1 . Taking account of the uncertainties associated with the top-Yukawa coupling and the estimation of backgrounds, we have found that the 95% CL region broadens i...

We study the Higgs-boson mass spectrum of a classical scale-invariant realization of the twoHiggs-doublet model (SI-2HDM). The classical scale symmetry of the theory is explicitly broken by quantum loop effects due to gauge interactions, Higgs self-couplings and topquark Yukawa couplings. We determine the allowed parameter space compatible with perturbative unitarity and electroweak precision data. Taking into account the LEP and the recent LHC exclusion limits on a Standard-Model-like Higgs boson H SM , we obtain rather strict constraints on the mass spectrum of the heavy Higgs sector of the SI-2HDM. In particular, if M H SM ∼ 125 GeV, the SI-2HDM strongly favours scenarios, in which at least one of the non-standard neutral Higgs bosons has a mass close to 400 GeV and is generically degenerate with the charged Higgs boson, whilst the third neutral Higgs scalar is lighter than ∼ 500 GeV.

We explore a new possibility of electroweak baryogenesis in the next-to-minimal supersymmetric standard model. In this model, a strong first-order electroweak phase transition can be achieved due to the additional singlet Higgs field. The new impact of its superpartner (singlino) on the baryon asymmetry is investigated by employing the closed-time-path formalism. We find that the CP violating source term fueled by the singlino could be large enough to generate the observed baryon asymmetry of the Universe without any conflicts with the current constraints from the non-observation of the Thallium, neutron and Mercury electric dipole moments.