arXiv subjects

Leandro Da Rold

Publications and source records attributed to Leandro Da Rold.

40 records · Page 3Linked to original sources

arXiv2006

Light custodians in natural composite Higgs models

We present a class of composite Higgs models arising from a warped extra dimension that can satisfy all the electroweak precision tests in a significant portion of their parameter space. A custodial symmetry plays a crucial role in keeping the largest corrections to the electroweak observables below their experimental limits. In these models the heaviness of the top quark is not only essential to trigger the electroweak symmetry breaking, but it also implies that the lowest top resonance and its custodial partners, the custodians, are significantly lighter than the other resonances. These custodians are the trademark of these scenarios. They are exotic colored fermions of electromagnetic charges 5/3, 2/3 and -1/3, with masses predicted roughly in the range 500-1500 GeV. We discuss their production and detection at the LHC.

hep-ph↗

arXiv2006

A custodial symmetry for Zbb

We show that a subgroup of the custodial symmetry O(3) that protects delta rho from radiative corrections can also protect the Zbb coupling. This allows one to build models of electroweak symmetry breaking, such as Higgsless, Little Higgs or 5D composite Higgs models, that are safe from corrections to Z-> bb. We show that when this symmetry protects Zbb it cannot simultaneously protect Ztt and Wtb. Therefore one can expect to measure sizable deviations from the SM predictions of these couplings at future collider experiments. We also show under what circumstances Zb_R b_R can receive corrections in the right direction to explain the anomaly in the LEP/SLD forward-backward asymmetry A^b_{FB}.

hep-ph↗

arXiv2005

The scalar and pseudoscalar sector in a five-dimensional approach to chiral symmetry breaking

We study the scalar and pseudoscalar sector in a five-dimenional model describing chiral symmetry breaking. We calculate the scalar and pseudoscalar two-point correlator, the mass spectrum and interactions. We also obtain the scalar and pseudoscalar contributions to the coefficients of the chiral lagrangian and determine the scalar form factor of the pseudo-Goldstone bosons. Most quantities show a good agreement with QCD.

hep-ph↗

arXiv2005

Chiral symmetry breaking from five dimensional spaces

Based on the AdS/CFT correspondence we study the breaking of the chiral symmetry in QCD using a simple five dimensional model. The model gives definite predictions for the spectrum of vector mesons, their decay constants and interactions as a function of one parameter related to the quark condensate. We calculate the coefficients $L_i$ of the low-energy QCD chiral lagrangian, as well as other physical quantities for the pions. All the predictions are shown to be in good agreement with the experimental data. We also show that they are robust under modifications of the 5D metric in the IR, and that some of them arise as a consequence of the higher-dimensional gauge symmetry. For example, at the tree-level, we find $M_ρ\simeq \sqrt{3} g_{ρππ} F_π$, $F_ρ\simeq \sqrt{3} F_π$ and BR($a_1\to πγ)=0$.

hep-ph↗