Higgs bosons in the two-doublet model involving <Emphasis Type="Italic">CP</Emphasis> violation

An effective two-doublet Higgs potential that involves complex-valued parameters and whose CP invariance is violated both explicitly and spontaneously is considered. The problem of diagonalizing the mass term of this potential at a local minimum is solved. The eigenstates of Higgs bosons and their mass spectrum are obtained for the special case of the two-doublet Higgs sector of the minimal supersymmetric model, where the CP invariance of the effective potential is violated owing to the interactions of the Higgs fields with the third-generation scalar quarks.     

Light Higgs boson in the two-doublet model featuring explicit <Emphasis Type="Italic">CP</Emphasis> violation

The most general form of an effective two-doublet Higgs potential whose parameters are complex-valued and whose CP invariance is violated explicitly in the minimal supersymmetric model caused by Higgs boson interaction with third-generation squarks is considered. Higgs boson states are obtained and their masses are calculated, along with the decay widths of the lightest Higgs boson and the cross section for its production, in the case of substantial mixing between the CP-even states h and H and the CP-odd state A.     

Analytic expressions for threshold corrections to the finite-temperature higgs potential in the minimal supersymmetric standard model

Within the minimal supersymmwtric standard model (MSSM) featuring an explicit CP violation, one-loop corrections to the parameters of the effective two-doublet potential are calculated at finite temperature for various scales of the mass parameters in the sector of soft supersymmetry breaking. It is shown that the splitting of scalar-quark masses has a strong effect on the effective parameters of the potential and that, in the limiting case where all mass parameters of the squark sector are degenerate and where the temperature is zero, the potential parameters reduce to the results obtained previously.     

CP violation in vector-like theories of weak interaction

In vector-like theories of weak interaction where CP is broken spontaneously through the vacuum, one can always find a proper CP transformation law for the physical particles that violates CP only in the Higgs sector, but not in the fermion gauge coupling.     

Triple and quartic interactions of Higgs bosons in the two-Higgs-doublet model with <Emphasis Type="Italic">CP</Emphasis>-violation

We consider the two-Higgs-doublet model with explicit CP-violation, where the effective Higgs potential is not CP-invariant at the tree level. The three neutral Higgs bosons of the model are the mixtures of CP-even and CP-odd bosons which exist in the CP-conserving limit of the theory. The mass spectrum and tree-level couplings of the neutral Higgs bosons to gauge bosons and fermions are significantly dependent on the parameters of the Higgs boson mixing matrix. We calculate the Higgs-gauge boson, Higgs-fermion, triple and quartic Higgs self-interactions in the MSSM with explicit CP-violation in the Higgs sector and CP-violating Yukawa interactions of the third generation scalar quarks. In some regions of the MSSM parameter space substantial changes of the self-interaction vertices take place, leading to significant suppression or enhancement of the multiple Higgs boson production cross sections. Received: 13 June 2002 / Revised version: 20 November 2002 / Published online: 14 March 2003     

Spontaneous CP violation in left-right symmetric gauge theories

Motivated by arguments in favour of spontaneous CP violation, we investigate the general conditions imposed by P and CP invariance on the Yukawa couplings in SU(2)_L × SU(2)_R × U(1) gauge theories. A complete discussion of these constraints is presented for two minimal Higgs sectors. In addition to the standard case of manifest CP invariance, we find two phenomenologically interesting models where the P and CP transformations are non-aligned in flavour and Higgs spaces. To a certain extent, P and CP invariance may be responsible for the existence of horizontal symmetries. An intimate connection between CP violation and the general flavour problem emerges.     

Supersymmetric corrections to the higgs sector in the minimal supersymmetric standard model featuring explicit <Emphasis Type="Italic">CP</Emphasis> violation

Explicit CP violation in the Higgs sector of the minimal supersymmetric standard model can be introduced owing to the interaction of Higgs bosons with third-generation scalar quarks. Supersymmetric corrections to effective-potential parameters at various values of the masses \(M_{\tilde Q} ,M_{\tilde U} \), and \(M_{\tilde D} \) are calculated by the effective-potential method. It is shown that, in this case, the potential parameters may differ strongly from those in the case of degenerate mass parameters of the scalar sector of the minimal supersymmetric standard model. This leads to a weak dependence of observables on the CP-violation phase.     

P-odd effectiveZγγγ interactions

A general analysis of the lowest-dimensionalP-oddZγγγ interaction is performed. It turns out that there are only two independent gauge invariant dimension-eight effective Lagrangians of such a type, similarly to theP-even case discussed earlier. It is shown, that such an effective interaction is naturally induced, at the twoloop level, within an extension of the standard model of electroweak interactions involving two-doubletCP-violating Higgs sector.     

K 0 → \bar K^0 and B 0 → \bar B^0 transitions in the minimal supersymmetric standard model involving explicit CP violation in the Higgs sector

Mixing in the systems of neutral K ⁰ and B ⁰ mesons is considered within the minimal supersymmetric standard model (MSSM) containing a type-II Yukawa sector and featuring an explicitCP violation in the Higgs potential. In the case of a strong mixing of CP-even and CP-odd states, the model admits the presence of a light charged Higgs boson. Basic mixing parameters are calculated. These include the mass difference Δm _LS between neutral kaons and the parameter ε, which characterizes the amount of an indirect CP violation (that is, that which arises owing to an ultraweak mixing of CP-invariant and CP-noninvariant components). In the limit of the low-energy one-loop approximation, it is shown that, for the K ⁰ mesons, the contribution of nonstandard-physics effects to the mass splitting of the neutral kaons and an indirect CP violation are very small and are weakly dependent on the mass of the charged Higgs boson. Under certain conditions, the nonstandard contributions for the B ⁰- $ \bar B_d^0 $ and B ⁰- $ \bar B_s^0 $ systems may become somewhat more substantial, which constrains the MSSM parameter space.     

Majorana neutrinos and CP violation in the leptonic sector

A set of weak-basis-independent necessary conditions is derived for CP conservation in the leptonic sector of the SU(2) × U(1) gauge theory with an arbitrary number of generations, when both Majorana and Dirac neutrino mass terms are present. In the case of two and three generations of left-handed Majorana neutrinos, weak-basis-independent conditions are given which are necessary and sufficient for CP invariance in the leptonic sector. It is also shown that for three or more generations of Majorana neutrinos, there may be CP violation even in the limit of complete neutrino-mass degeneracy.     

Constraints on electroweak baryogenesis in models involving an extended Higgs sector

Consequences for electroweak baryogenesis within models featuring an extended Higgs sector are analyzed. The phenomenology of extensions of the scalar sector in the Standard Model and its significance for the electroweak phase transition are studied. Conditions for the effective potential of the two-doublet model that lead to a strong first-order phase transition necessary for generating the observed baryon-antibaryon asymmetry are determined.     

Mixing of <Emphasis Type="Italic">K</Emphasis><Superscript>0</Superscript> and <Emphasis Type="Italic">B</Emphasis><Superscript>0</Superscript> neutral mesons within the minimum supersymmetry model

Mixing of K ⁰ and B ⁰ mesons is studied in the scope of the minimum supersymmetry model (MSSM) with a type II Yukawa sector and explicit violation of CP invariance in the Higgs potential. The mixing parameters Δm _LS and ? are calculated in the limit of the low-energy four-fermion approximation with a charged Higgs boson exchange. It is shown that supersymmetric effects are very small for K ⁰ mesons and may be quite significant for B _s ⁰ and B _d ⁰ mesons, which imposes constraints on the MSSM parameter space.     

Model-independent analysis of <Emphasis Type="Italic">CP</Emphasis> violation effects in decays of the Higgs boson into a Pair of the <Emphasis Type="Italic">W</Emphasis> and <Emphasis Type="Italic">Z</Emphasis> bosons

Effects of CP and T invariance violation are studied in the most general interaction of the Higgs boson with the intermediate vector W ^± and Z bosons. Various angular distributions of the cascade decay Φ → W ⁺ W ^?/ZZ → 4 of fermions in the transversity and helicity systems are calculated, and asymmetries are constructed and evaluated. It is shown that studying the azimuthal angle distribution of the process Φ → ZZ → (e ^? e ⁺)(μ^?μ⁺) in the transversity system is effective for measuring the spatial parity of the Higgs boson.     

The other natural two Higgs doublet model

We characterize models where electroweak symmetry breaking is driven by two light Higgs doublets arising as pseudo-Nambu-Goldstone bosons of new dynamics above the weak scale. They represent the simplest natural two Higgs doublet alternative to supersymmetry. We construct their low-energy effective Lagrangian making only few specific assumptions about the strong sector. These concern their global symmetries, their patterns of spontaneous breaking and the sources of explicit breaking. In particular we assume that all the explicit breaking is associated with the couplings of the strong sector to the Standard Model fields, that is gauge and (proto)-Yukawa interactions. Under those assumptions the scalar potential is determined at lowest order by very few free parameters associated to the top sector. Another crucial property of our scenarios is the presence of a discrete symmetry, in addition to custodial SO(4), that controls the T-parameter. That can either be simple CP or a Z₂ that distinguishes the two Higgs doublets. Among various possibilities we study in detail models based on SO(6)/SO(4) × SO(2), focussing on their predictions for the structure of the scalar spectrum and the deviations of their couplings from those of a generic renormalizable two Higgs doublet model.     

Experimental signatures of fermiophobic Higgs bosons

The most general Two Higgs Doublet Model potential without explicit CP violation depends on 10 real independent parameters. Excluding spontaneous CP violation results in two 7 parameter models. Although both models give rise to 5 scalar particles and 2 mixing angles, the resulting phenomenology of the scalar sectors is different. If flavour changing neutral currents at tree level are to be avoided, one has, in both cases, four alternative ways of introducing the fermion couplings. In one of these models the mixing angle of the CP even sector can be chosen in such a way that the fermion couplings to the lightest scalar Higgs boson vanishes. At the same time it is possible to suppress the fermion couplings to the charged and pseudo-scalar Higgs bosons by appropriately choosing the mixing angle of the CP odd sector. We investigate the phenomenology of both models in the fermiophobic limit and present the different branching ratios for the decays of the scalar particles. We use the present experimental results from the LEP collider to constrain the models. Received: 21 July 1999 / Revised version: 6 September 1999 / Published online: 3 November 1999     

Supersymmetric Higgs boson decays in the MSSM with explicit <Emphasis Type="Italic">CP</Emphasis> violation

Decays into neutralinos and charginos are among the most accessible supersymmetric decay modes of Higgs particles in most supersymmetric extensions of the standard model. In the presence of explicitly CP violating phases in the soft breaking sector of the theory, the couplings of Higgs bosons to charginos and neutralinos are in general complex. Based on a specific benchmark scenario of CP violation, we analyze the phenomenological impact of explicit CP violation in the minimal supersymmetric standard model on these Higgs boson decays. The presence of CP violating phases could be confirmed either directly through the measurement of a CP odd polarization asymmetry of the produced charginos and neutralinos, or through the dependence of CP even quantities (branching ratios and masses) on these phases. Received: 18 April 2002 / Published online: 26 July 2002     

On the strong-CP problem in models with several Higgs multiplets and supersymmetry

We point out that the strong-CP problem becomes even more pressing in the context of weak models where CP violation originates in the Higgs sector. θ renormalization is numerically too large at the one-loop level and even divergent at the two-loop level. When supersymmetry (SUSY) is introduced, many more possible sources for CP violation open up. θ renormalization could stay finite in perturbation theory, however, we find that the one-loop result turns out to be too large by orders of magnitude unless SUSY fields like gauginos and higgsinos are highly degenerate in mass or SUSY breaking proceeds in a very special way, or a Peccei-Quinn symmetry holds leading to superlight axions.     

One-loop wave-function renormalization corrections in the scalar sector of the Minimal Supersymmetric Standard Model

One-loop field-renormalization corrections for the two-doublet Higgs potential of the Minimal Supersymmetric Standard Model are obtained within the formalism of finite-temperature quantum field theory. The inclusion of these corrections is necessary for describing the evolution of potential parameters with temperature and affects the electroweak phase transition. In the limiting case where all mass parameters of the squark sector are degenerate and where the temperature is zero, the potential parameters coincide with the results obtained previously.     

Critical parameters of the temperature evolution of the two-doublet potential in the minimal supersymmetric Standard Model

Finite-temperature properties of the two-doublet extension of the scalar sector of the Standard Model and its special features concerning the electroweak phase transition are considered. Critical conditions for the temperature evolution of the effective potential in the two-doublet model that lead to a strong first-order phase transition, which is necessary for the generation of the observed baryon-antibaryon asymmetry, are determined.     

Gauge theoretical realization of the superweak model of CP violation

It is pointed out that the presence in a gauge theory of vector bosons or left-over Higgs bosons with a weak interaction strength of the order of10^?11G_E and which have CPviolating couplings to the strangeness-changing neutral current, will lead to the superweak model of CP violation. An example of such a theory, based on the gauge group SU (2) ?U(1), is given.