Browsing by Author "Panico, Giuliano"

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    Effective Action and Holography in 5D Gauge Theories
    (2007-05-15T12:17:54Z) Panico, Giuliano; Wulzer, Andrea; Physics; Elementary Particle Theory
    We apply the holographic method to 5D gauge theories on the warped interval. Our treatment includes the scalars associated with the fifth gauge field component, which appear as 4D Goldstone bosons in the holographic effective action. Applications are considered to two classes of models in which these scalars play an important role. In the Composite-Higgs (and/or Gauge-Higgs Unification) scenario, the scalars are interpreted as the Higgs field and we use the holographic recipe to compute its one-loop potential. In AdS/QCD models, the scalars are identified with the mesons and we compute holographically the Chiral Perturbation Theory Lagrangian up to p^4 order. We also discuss, using the holographic perspective, the effect of including a Chern-Simons term in the 5D gauge Lagrangian. We show that it makes a Wess-Zumino-Witten term to appear in the holographic effective action.
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    The electroweak phase transition on orbifolds with gauge-Higgs unification
    (2005) Panico, Giuliano; Serone, Marco; Physics; Elementary Particle Theory
    The dynamics of five dimensional Wilson line phases at finite temperature is studied in the one-loop approximation. We show that at temperatures of order T ~ 1/L, where L is the length of the compact space, the gauge symmetry is always restored and the electroweak phase transition appears to be of first order. Particular attention is devoted to the study of a recently proposed five dimensional orbifold model (on S1/Z2) where theWilson line phase is identified with the Higgs field (gauge-Higgs unification). Interestingly enough, an estimate of the leading higher-loop "daisy" (or "ring") diagram contributions to the effective potential in a simple five dimensional model, seems to suggest that the electroweak phase transition can be studied in perturbation theory even for Higgs masses above the current experimental limit of 114 GeV. The transition is still of first order for such values of the Higgs mass. If large localized gauge kinetic terms are present, the transition might be strong enough to give baryogenesis at the electroweak transition.
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    Electroweak Symmetry Breaking and Precision Tests with a Fifth Dimension
    (2006-06-13T11:33:38Z) Panico, Giuliano; Serone, Marco; Wulzer, Andrea; Physics; Elementary Particle Theory
    We perform a complete study of flavour and CP conserving electroweak observables in a slight refinement of a recently proposed five--dimensional model on R^4XS^1/Z_2, where the Higgs is the internal component of a gauge field and the Lorentz symmetry is broken in the fifth dimension. Interestingly enough, the relevant corrections to the electroweak observables turn out to be of universal type and essentially depend only on the value of the Higgs mass and on the scale of new physics, in our case the compactification scale 1/R. The model passes all constraints for 1/R > 4.7 TeV at 90% C.L., with a moderate fine--tuning in the parameters. The Higgs mass turns out to be always smaller than 200 GeV although higher values would be allowed, due to a large correction to the T parameter. The lightest non-SM states in the model are typically colored fermions with a mass of order 1-2 TeV.
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    A model of electroweak symmetry breaking from a fifth dimension
    (2005) Panico, Giuliano; Serone, Marco; Wulzer, Andrea; Physics; Elementary Particle Theory
    We reconsider the idea of identifying the Higgs field as the internal component of a gauge field in the flat space [FORMULA] by relaxing the constraint of having unbroken SO(4,1) Lorentz symmetry in the bulk. In this way, we show that the main common problems of previous models of this sort, namely the prediction of a too light Higgs and top mass, as well as of a too low compactification scale, are all solved. We mainly focus our attention on a previously constructed model. We show how, with few minor modifications and by relaxing the requirement of SO(4,1) symmetry, a potentially realistic model can be obtained with a moderate tuning in the parameter space of the theory. In this model, the Higgs potential is stabilized and the hierarchy of fermion masses explained.