M. Perez-Victoria

Effects of new leptons in Electroweak Precision Data

We obtain limits on generic vectorlike leptons at the TeV scale from electroweak precision tests. These limits are complementary to the ones obtained from lepton flavor violating processes. In general, the quality of the global electroweak fit is comparable to the one for the standard model. In the case of an extra neutrino singlet mixing with the muon or electron, the global fit allows for a relatively large Higgs mass (M{sub H} < or approx. 260 GeV at 90% C.L.), thus relaxing the tension between the direct CERN LEP limit and the standard model fit.

Electroweak Limits on General New Vector Bosons

We study extensions of the Standard Model with general new vector bosons. The full Standard Model gauge symmetry is used to classify the extra vectors and constrain their couplings. We derive the corresponding effective Lagrangian, valid at energies lower than the mass of the extra vectors, and use it to extract limits from electroweak precision observables, including LEP 2 data. We consider both universal and nonuniversal couplings to fermions. We study the interplay of several extra vectors, which can have the effect of opening new regions in parameter space. In particular, it allows to explain the anomaly in the bottom forward-backward asymmetry with perturbative couplings. Finally, we analyze quantitatively the implications for the Higgs mass.

Probing the Tevatron \( t\overline t \) asymmetry at LHC

Weusean effective operator framework to study the contributions to the Tevatron

Simple models for the top asymmetry: constraints and predictions

t\overline t

No like-sign tops at Tevatron: Constraints on extended models and implications for the tt¯ asymmetry

asymmetry from arbitrary vector bosons and scalars, and compare with their effect on the

Shaping the top asymmetry

t\overline t

Electroweak Breaking on a Soft Wall

tail at LHC. Our study shows, for example, that models reproducing the

Asymmetries in tt¯ production: LHC versus Tevatron

t\overline t

Observable effects of general new scalar particles

asymmetry by exchange of Z′ and W′ bosons or colour-triplet scalars lead to a large enhancement in the

Combining searches of Z′ and W′ bosons

t\overline t