Charged lepton electric dipole moments with localized leptons and new Higgs doublet in the two Higgs doublet model

We study the electric dipole moments of the leptons in the split fermion scenario, in the two Higgs doublet model, where the new Higgs scalars are localized around the origin in the extra dimension, with the help of the localizer field. We observe that the numerical value of the electric dipole moment of the electron (muon, tau) is of the order of the magnitude of 10^-31 (10^-24, 10^-22) (e cm), and this quantity is sensitive to the new Higgs localization in the extra dimension.     

Lepton flavor violating Z→l1 +l2 - decay in the split fermion scenario in the two Higgs doublet model

We predict the branching ratios of the Z→e^±μ^±, Z→e^±τ^± and Z→μ^±τ^± decays in the framework of the 2HDM, in the split fermion scenario. We observe that the branching ratios are not sensitive to a single extra dimension; however, this sensitivity is considerably large for two extra dimensions.     

Electric dipole moments of charged particles

The existence of an electric dipole moment (edm) on a fundamental atomic particle would imply violation of both parity and time-reversal invariance. An edm on a neutral particle is detectable through its interaction with an applied electric field. The search for edms on charged particles such as the nucleus or the electron is made difficult by their acceleration in an electric field; conversely, a charged particle in equilibrium must be shielded from the field and the edm interaction will then vanish. A number of ingenious ways around this shielding theorem are discussed, as are the use of polar molecules to amplify the residual edm interactions. A range of atomic and molecular beam and optical pumping experiments are described and the results tabulated. The implications for particle theories beyond the standard model are briefly summarized.     

Electric and weak electric dipole form factors for heavy fermions in a general two Higgs doublet model

The electric and weak electric dipole form factors for heavy fermions are calculated in the context of the most general two Higgs doublet model (2HDM). We find that a large top mass can produce a significant enhancement of the electric dipole form factor in the case of the b and c quarks. This effect can be used to distinguish between different 2HDM scenarios. Received: 30 April 1999 / Revised version: 23 Juny 1999 / Published online: 14 October 1999     

The effect of the location of the new Higgs doublet on the radiative lepton flavor violating decays in the split fermion scenario

We study the branching ratios of the lepton flavor violating processes μ→eγ, τ→eγ and τ→μγ in the split fermion scenario, with the assumption that the new Higgs doublet is restricted to the 4D brane (thin bulk) in one and two extra dimensions, in the framework of the two Higgs doublet model. We observe that the branching ratios are sensitive to the location of the 4D brane and, in the second case, the width of the thin bulk, especially for the μ→eγ decay.     

TheZ-width in the two Higgs doublet model

Effects from an extended Higgs sector on the partial widths \(\Gamma _{{\rm Z} \to b\bar b} \) and \(\Gamma _{{\rm Z} \to \tau ^ + \tau ^ - } \) are analysed with emphasis on enhanced Yukawa couplings to the fermions with the weak isospinT ₃=?1/2. Contributions from charged and neutral Higgs bosons are incorporated. Vertex corrections from a heavy top quark and from charged Higgs bosons are always negative. One can however find regions in the parameter space where neutral Higgs bosons lead to positive vertex corrections. The charged Higgs bosons decouple from the ratio \(\Gamma ^{_{{\rm Z} \to \tau ^ + \tau ^ - } } /\Gamma ^{_{{\rm Z} \to \mu ^ + \mu ^ - } } \) if their mass is beyond 80 GeV. This ratio is then sensitive to the neutral sector only.     

Search for charged Higgs bosons at LEP in general two Higgs doublet models

A search for pair-produced charged Higgs bosons was performed in the data collected by the DELPHI detector at LEP II at centre-of-mass energies from 189 GeV to 209 GeV. Five different final states, , , , and were considered, accounting for the major expected decays in type I and type II Two Higgs Doublet Models. No significant excess of data compared to the expected Standard Model processes was observed. The existence of a charged Higgs boson with mass lower than 76.7 GeV/c² (type I) or 74.4 GeV/c² (type II) is excluded at the 95% confidence level, for a wide range of the model parameters. Model independent cross-section limits have also been calculated.Received: 30 September 2003, Revised: 12 February 2004, Published online: 8 April 2004     

Anomalous moments of heavy charged leptons

If leptons and quarks are composite particles we expect them to have anomalous moments: an anomalous magnetic moment and an analogue of this with respect to the weak neutral current. If these moments are suppressed by chiral symmetry they will have sizeable values only for heavy fermions, e.g. for fermions of the fourth generation. The forward-backward asymmetry of e⁺e⁻ → f̄f on the Z⁰ resonance is particularly suited for detecting the anomalous “weak magnetic” moment of f if f is the charged lepton of the fourth generation. Under favourable circumstances this moment may lead to a 10% effect.     

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.     

Reparameterization of the scalar potential in the two Higgs doublet model

In the two Higgs doublet model with no additional symmetries in the scalar sector (different from the gauge and Lorentz symmetries), it is customary to reparameterize the model by rotating the scalar doublets so that one of the vacuum expectation values vanishes. It is well known that the Yukawa sector of the model is unaffected by such a transformation. Notwithstanding this, since the Higgs potential must also be transformed, it is necessary to show that such a sector is also unaltered in its physical content. We demonstrate that the physical content of the potential is invariant even when the charge conjugation symmetry is demanded. PACS 12.60.Fr; 11.30.Er; 11.15.Ex; 11.30.Hv     

Electric dipole moments in the generic supersymmetric standard model

The generic supersymmetric standard model is a model built from a supersymmetrized standard model field spectrum and the gauge symmetries only. The popular minimal supersymmetric standard model differs from the generic version in having R parity imposed by hand. We review an efficient formulation of the model and some of the recently obtained interesting phenomenological features, focusing on one-loop contributions to fermion electric dipole moments.     

The effects of lepton KK modes on the electric dipole moments of the leptons in the Randall–Sundrum scenario

We study the charged lepton electric dipole moments in the Randall–Sundrum model where the leptons and the gauge fields are accessible to the extra dimension. We observe that the electric dipole moment of the electron (muon; tau) reaches a value of the order of 10^-26 e cm (10^-20 e cm; 10^-20 e cm) with the inclusion of the lepton KK modes.     

Dimensional reduction of the two Higgs doublet model at high temperature

Dimensional reduction and effective field theory methods are applied to the Two Higgs Doublet Model at finite temperature. A sequence of two effective three-dimensional field theories which are valid on successively longer distance scales is constructed. The resulting Lagrangian can be used to study different aspects of the phase transition in this model as well as the sphaleron rate immediately after the phase transition. Received: 14 March 1999 / Published online: 22 October 1999     

Electric dipole moments of nuclei

Recent calculations by Sushkov, Flambaum and Khriplovich have suggested that the existence of the possibility of kaon exchange within nuclei allows nuclear electric dipole moments within the standard model to be enhanced substantially over those of nucleons. This suggestion is analysed carefully and it is found that the constraints of chiral symmetry, which were not correctly included in the earlier calculation, reduce this prediction substantially.