Top quark forward-backward asymmetry from the 3−3−13-3-1 model

The forward-backward asymmetry $A_{FB}$ in top quark pair production, measured at the Tevatron, is probably related to the contribution of new particles. The Tevatron result is more than a $2\sigma$ deviation from the standard model prediction and motivates the application of alternative models introducing new states. However, as the standard model predictions for the total cross section $\sigma_{tt}$ and invariant mass distribution $M_{tt}$ for this process are in good agreement with experiments, any alternative model must reproduce these predictions. These models can be placed into two categories: One introduces the s-channel exchange of new vector bosons with chiral couplings to the light quarks and to the top quark and another relies on the t-channel exchange of particles with large flavor-violating couplings in the quark sector. In this work we employ a model which introduces both s- and t-channel nonstandard contributions for the top quark pair production in proton antiproton collisions. We use the minimal version of the $SU(3)_C \otimes SU(3)_L \otimes U (1)_X$ model (3-3-1 model) that predicts the existence of a new neutral gauge boson, called $Z^\prime$. This gauge boson has both flavor-changing couplings to up and top quarks and chiral coupling to the light quarks and to the top quark. This very peculiar model coupling can correct the $A_{FB}$ for top quark pair production for two ranges of $Z^\prime$ mass while leading to cross section and invariant mass distribution quite similar to the standard model ones. This result reinforces the role of the 3-3-1 model for any new physics effect.Comment: 12 pages, 4 figures, 2 table

Charged bilepton pair production at LHC including exotic quark contribution

AbstractThe production of W+W− pair in hadron colliders was calculated up to loop corrections by some authors in the Electroweak Standard Model (SM) framework. This production was also calculated, at the tree level, in some extensions of the SM such as the vector singlet, the fermion mirror fermion and the vector doublet models by considering the contributions of new neutral gauge bosons and exotic fermions. The obtained results for e+e− and pp collisions pointed out that the new physics contributions are quite important. This motivates us to calculate the production of a more massive charged gauge boson predicted by the SU(3)C×SU(3)L×U(1)X model (3-3-1 model). Thus, the aim of the present paper is to analyze the role played by of the extra gauge boson Z′ and of the exotic quarks, predicted in the minimal version of the 3-3-1 model, by considering the inclusive production of a pair of bileptons (V±) in the reaction p+p→V++V−+X, at the Large Hadron Collider (LHC) energies.Our results show that the correct energy behavior of the elementary cross section follows from the balance between the contributions of the extra neutral gauge boson with those from the exotic quarks. The extra neutral gauge boson induces flavor-changing neutral currents (FCNC) at tree level, and we have introduced the ordinary quark mixing matrices for the model when the first family transforms differently to the other two with respect to SU(3)L. We obtain a huge number of heavy bilepton pairs produced for two different values of the center of mass energy of the LHC

Production of Charged Higgs Bosons in a 3-3-1 Model at the CERN LHC

We perform a study of the charged Higgs production from an $SU(3)_{C}\otimes SU(3)_{L}\otimes U(1)_{X}$ model with right-handed neutrinos, postulating a custodial symmetry which reduces the number of free parameters in the scalar potential. We compute the cross sections for charged scalars for typical and new production modes. One of the new $SU(3)_{L}$ neutral gauge bosons, $Z^{\prime}$, affects some production cross sections distinguishing the model from other Standard Model extensions like, for example, the Minimal Supersymmetric Standard Model and general two Higgs doublets models. The interplay between the Higgs sector of the model and that $Z^{\prime}$ gauge boson enhances substantialy all the production rates of the lightest charged Higgs boson, $H_{1}^{\pm}$, at hadron colliders compared to the MSSM. We found that a large portion of the parameters space can be probed at the LHC running at 14 TeV center-of-mass energy in the associated $pp\rightarrow W^{\pm}H_{1}^{\mp}+X$ production channel in the low luminosity run stage of the experiment.Comment: 30 pages, 20 figures, accepted for publication in Phys. Rev.

Explaining the Higgs Decays at the LHC with an Extended Electroweak Model

We show that the recent discovery of a new boson at the LHC, which we assume to be a Higgs boson, and the observed enhancement in its diphoton decays compared to the SM prediction, can be explained by a new doublet of charged vector bosons from an extended electroweak gauge sector model with SU(3)_C\otimesSU(3)_L\otimesU(1)_X symmetry. Our results show a good agreement between our theoretical expected sensitivity to a 126--125 GeV Higgs boson and the experimental significance observed in the diphoton channel at the 8 TeV LHC. Effects of an invisible decay channel for the Higgs boson are also taken into account, in order to anticipate a possible confirmation of deficits in the branching ratios into $ZZ^*$, $WW^*$, bottom quarks, and tau leptons.Comment: 16 pages, 5 figure