A. Méndez

Lepton flavour non-conservation at high energies in a superstring inspired standard model

Abstract We analyze some interesting phenomenological consequences of a class of models which extend the standard model by adding new neutral fermions. Such might arise in some models inspired on the heterotic superstring which have naturally light neutrinos. In these models it is possible to have sizable flavour changing decays of the Z to charged lepton pairs which might be detectable at SLC and/or LEP.

Specifically Supersymmetric Contribution to Electric Dipole Moments

Abstract We discuss a source of CP violation which is specific to supersymmetric theories. CP violating phases appear in the mass matrix of the gauge and Higgs fermions. We estimate its effect on the electric dipole moment of the electron and the neutron. Their magnitude is found to be close to the experimental upper bounds.

Signals of CP violation in the Higgs sector

Abstract We study possible ways of unraveling a CP non-invariant Higgs sector through the interactions of Higgs bosons with gauge bosons. We derive some general sum rules for the couplings and apply our results to the two-Higgs-doublet model.

Electromagnetic properties of the tau lepton from Z0 decay

Abstract We explore the potentialities of the radiative decay Z→τ + τ − γ at Z factories to constrain and eventually measure the magnetic moment and the electric dipole moment of the τ lepton. In particular, we use existing LEP data to bound both static quantities in a kinematic domain not accesible in previous experiments.

QCD corrections to the charged Higgs boson hadronic width

Abstract We compute the O(α s ) QCD corrections arising from virtual gluon exchange and real gluon emission to the hadronic width of the charged Higgs boson in the context of a model with two Higgs doublets.

On the g−2 and the pp→Z0→ℓ+ℓ−γ events

Abstract Different models have been proposed to explain the unexpected abudance of the Z 0 →e + e − γ events in the SPPS experiments. We show that the anomalous magnetic moments of leptons impose severe constraints on these models. These constraints are only avoided for very specific effective couplings.

Low energy CP violation in broken supersymmetry

Abstract We investigate the CP violation effects in supersymmetry broken models, due to the exchange of new fermions (gauginos and higgsinos). When the real part of the K 0 − K 0 amplitude is compatible with the experimental value, the possible imaginary part is too small to account for the ϵ parameter. In contrast, the experimental bounds on the ϵ′ parameter and the electric dipole moments, and especially the θ parameter, impose in general severe constraints on the possible CP violating phases. However, in some specific models there are extra suppression factors, leaving those phases essentially unconstrained except perhaps for the θ parameter.

On the

Abstract Different models have been proposed to explain the unexpected abudance of the Z 0 →e + e − γ events in the SPPS experiments. We show that the anomalous magnetic moments of leptons impose severe constraints on these models. These constraints are only avoided for very specific effective couplings.

g-2

Abstract We examine mechanisms for producing neutrino magnetic moments from a wide class of particle theories which are extensions of the standard model. We show that it is difficult to naturally obtain a moment greater than ∼ 10 −2 electron Bohr magnetons. Thus models of phenomena requiring moments of order ∼ 10 −10 magnetons, such as those proposed as a resolution to the solar neutrino puzzle, are in conflict with current perceptions in particle physics.

and the

Abstract For parity conserving, inclusive reactions of type spin 1 2 + unpolarized → spin 1 2 + anything, we define a set of seven spin rotation parameters, as a generalization of the parameters P, R, A of Wolfenstein. They constitute, with the differential cross section, the whole phenomenological information on this type of reactions for each value of total energy, momentum transfer, and missing mass. Their measurement procedure, by correlated asymmetries of initial and final polarizations, and their allowed positivity domain are explicitly discussed.