F. del Aguila

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.

Vector-like fermion and standard Higgs production at hadron colliders

Vector-like fermions are characterized by large neutral current decay rates, in particular into Higgs bosons. If they exist, their clear signals at hadron colliders open a window to Higgs detection, especially to the intermediate Higgs mass region. We discuss in some detail rates and signatures for simple cases.

Low-energy models with two supersymmetries

Abstract Realistic models of low-energy physics with two supersymmetries are constructed. Several mechanisms for providing large mirror fermion masses are given in models with gauge groups SU(3) × SU(2) × U(1) and SU(3) × SU(4) × U(1). It is found that the supersymmetry breaking scale must be significantly larger than the W-boson mass. Although none of the models is fully natural, each predicts that mirror fermions should soon be discovered. While the ordinary and mirror squarks and sleptons tend to be very heavy, some gauginos or mirror gauginos are probably light. The models offer prospects for eventual unification into finite grand unified theories.

Renormalization group analysis of extended electroweak models from the heterotic string

Abstract Extended electroweak models need new parameters (including new renormalization-induced gauge-mixing angles) to fix the gauge currents. We present the renormalization group predictions for these parameters in all heterotic string models with one extra, neutral, gauge boson at low energy. The possible matter contents, consistent with perturbative unification and low-energy physics, are determined for any model.

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.

Correlation between MZ, and mt bounds (I). Neutral current data☆

Abstract We discuss present neutral current data constraints (combined with M W and M Z measurements) on m t (and m H ) in the minimal gauge extension of the standard model. The extra gauge boson mass M Z , is the only new parameter (for fixed new gauge couplings λ and θ 1 ). Fits performed with M Z , and m t free, translate into allowed regions in the M Z ,− m t plane where the M Z , lower bound is correlated with the m t upper bound. As a consequence, the m t upper bound in extended electroweak models is stronger (lower) than the one obtained in the minimal standard model, and coincides with it in the limits M Z , → ∞. The influence of the different pieces of data on the fits is also discussed. We briefly comment on other constraints, such as those from charged current data and direct production at large hadron colliders.

Light scalars in N=1 locally supersymmetric theories

Abstract The coupling of supersymmetric Yang-Mills theories to supergravity generally leads to scalars acquiring tree level masses comparable to the gravitino mass. It is shown how to avoid such tree level masses. Radiative scalar masses are estimated, and provide a cutoff dependent upper bound on the gravitino mass of O(106−109) GeV. In many models the supersymmetry violations in the particle spectrum are governed by the gravitino mass which should therefore be heavier than O(20) GeV.

The electron anomalous magnetic moment in unbroken supergravity

Abstract We compute the lowest order (in the gravitational coupling constant) contribution of a graviton and a massless gravitino to ( g -2) e . Both contributions are shown to be finite but regularization dependent. They cancel each other when (supersymmetric) dimensional reduction is used.

MZ′ mass bounds from neutrino-hadron neutral current data and a precise MZ measurement

Abstract We study the constraints on the minimal (gauge) extension of the standard model from ν-q neutral current data. Using α, Gμ and MZ (with the present accuracy) as input parameters, we find that previous bounds on MZ′ are strengthened by ∼ 10% [MZ′>555 GeV (90% CL) for mt>77 GeV and mH