L. Basso

Renormalization group equation study of the scalar sector of the minimal B-L extension of the standard model

We present the complete set of renormalization group equations at one loop for the nonexotic minimal U(1) extension of the standard model (SM). It includes all models that are anomaly-free with the SM fermion content augmented by one right-handed neutrino per generation. We then pursue the numerical study of the pure B-L model, deriving the triviality and vacuum stability bounds on an enlarged scalar sector comprising one additional Higgs singlet field with respect to the SM.

Probing the charged Higgs boson at the LHC in the CP-violating type-II 2HDM

A bstractWe present a phenomenological study of a CP-violating two-Higgs-doublet Model with type-II Yukawa couplings at the Large Hadron Collider (LHC). In the light of recent LHC data, we focus on the parameter space that survives the current and past experimental constraints as well as theoretical bounds on the model. Once the phenomeno-logical scenario is set, we analyse the scope of the LHC in exploring this model through the discovery of a charged Higgs boson produced in association with a W boson, with the former decaying into the lightest neutral Higgs and a second W state, altogether yielding a

Precision tests of unitarity in leptonic mixing

b\bar{b}{W^{+}}{W^{-}}

Enhancing

signature, of which we exploit the W+W− semileptonic decays.

h \to \gamma \gamma

In the light of the recent LHC data, we study precision tests sensitive to the violation of lepton universality, in particular the violation of unitarity in neutrino mixing. Keeping all data we find no satisfactory fit, even allowing for violations of unitarity in neutrino mixing. Leaving out from the hadronic forward-backward asymmetry at LEP, we find a good fit to the data with some evidence of lepton universality violation at the level.

with staus in SUSY models with extended gauge sector

We discuss the impact on the stau masses of the additional D-terms in U(1)-extended MSSM models. We show, explicitly for the B-L-SSM, that these contributions can play a crucial role in the explanation of the enhanced diphoton decay rate of a SM-like Higgs particle around 125 GeV. Even in the most constrained scenario with universal scalar and gaugino masses, it is possible to obtain a sizable enhancement and, in addition, the correct relic density for the LSP. Furthermore, a lighter CP-even scalar that could fit the LEP excess at 98 GeV is viable.

Dark matter scenarios in the minimal SUSY B − L model

A bstractWe perform a study of the dark matter candidates of a constrained version of the minimal R-parity-conserving supersymmetric model with a gauged U(1)B−L. It turns out that there are four additional candidates for dark matter in comparison to the MSSM: two kinds of neutralino, which either correspond to the gaugino of the U(1)B−L or to a fermionic bilepton, as well as “right-handed” CP-even and -odd sneutrinos. The correct dark matter relic density of the neutralinos can be obtained due to different mechanisms including new co-annihilation regions and resonances. The large additional Yukawa couplings required to break the U(1)B−L radiatively often lead to large annihilation cross sections for the sneutrinos. The correct treatment of gauge kinetic mixing is crucial to the success of some scenarios. All candidates are consistent with the exclusion limits of Xenon100.

A renormalization group analysis of the Hill model and its HEIDI extension

Abstract The parameter space of the simplest extension of the standard model is studied in the light of the 125 GeV Higgs boson discovery. The Hill model extends the scalar sector of the standard model with a real singlet, that mixes with the standard model Higgs boson only via cubic interactions. The two-loop standard model renormalization group equations are completed with the one-loop Hill equations. Stability up to the Planck scale is possible without tension with the other parameters. An extension with more singlet fields, in particular a higher-dimensional (HEIDI) field, is presented.

Theoretical constraints on the couplings of non-exotic minimal

We have combined perturbative unitarity and renormalisation group equation arguments in order to find a dynamical way to constrain the space of the gauge couplings of the so-called “Minimal Z′ Models”. We have analysed the role of the gauge couplings evolution in the perturbative stability of the two-to-two body scattering amplitudes of the vector and scalar sectors of these models and we have shown that perturbative unitarity imposes an upper bound that is generally stronger than the triviality constraint. We have also demonstrated how this method quantitatively refines the usual triviality bound in the case of benchmark scenarios such as the U(1)χ, the U(1)R or the “pure” U(1)B−L extension of the Standard Model. Finally, a description of the underlying model structure in Feynman gauge is provided.

Z'

We have combined perturbative unitarity and renormalization group equation arguments in order to find a dynamical way to constrain the g? 1 coupling of the minimal B–L extension of the standard model. We have analysed the role of the g? 1 coupling evolution in the perturbative stability of the two-to-two body scattering amplitudes of the vector boson and scalar sectors of the model, and we have shown that perturbative unitarity imposes an upper bound on the B–L gauge coupling. We have made a comparison between this criterion and the triviality arguments, showing that our procedure substantially refines the triviality bounds.