Riccardo Rattazzi - Academia.edu (original) (raw)

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Papers by Riccardo Rattazzi

Nuclear Physics B, 2006

We stress that the lack of direct evidence for supersymmetry forces the soft mass parameters to l... more We stress that the lack of direct evidence for supersymmetry forces the soft mass parameters to lie very close to the critical line separating the broken and unbroken phases of the electroweak gauge symmetry. We argue that the level of criticality, or fine-tuning, that is needed to escape the present collider bounds can be quantitatively accounted for by assuming that

We review CP violation in various extensions of the electroweak sector of the Standard Model. A p... more We review CP violation in various extensions of the electroweak sector of the Standard Model. A particular emphasis is put on supersymmetric models. We describe the two CP problems of supersymmetry, concerning dNd_NdN and epsilonK\epsilon_KepsilonK. We critically review the various mechanisms that have been suggested to solve these problems: exact universality, approximate CP symmetry, alignment, approximate universality and heavy squarks.

Journal of High Energy Physics, 2003

Journal of High Energy Physics, 2014

We derive model-independent lower bounds on the stress tensor central charge C_T in terms of the ... more We derive model-independent lower bounds on the stress tensor central charge C_T in terms of the operator content of a 4-dimensional Conformal Field Theory. More precisely, C_T is bounded from below by a universal function of the dimensions of the lowest and second-lowest scalars present in the CFT. The method uses the crossing symmetry constraint of the 4-point function, analyzed

Journal of High Energy Physics, 2006

Journal of High Energy Physics, 2004

Journal of High Energy Physics, 2010

The hierarchy problem and the electroweak data, together, provide a plausible motivation for cons... more The hierarchy problem and the electroweak data, together, provide a plausible motivation for considering a light Higgs emerging as a pseudo-Goldstone boson from a strongly-coupled sector. In that scenario, the rates for Higgs production and decay differ significantly from those in the Standard Model. However, one genuine strong coupling signature is the growth with energy of the scattering amplitudes among

Journal of High Energy Physics - J HIGH ENERGY PHYS, 2011

We consider a generic composite Higgs model based on the coset SO(5) /SO(4) and study its phenome... more We consider a generic composite Higgs model based on the coset SO(5) /SO(4) and study its phenomenology beyond the leading low-energy effective lagrangian approximation. Our basic goal is to introduce in a controllable and simple way the lowest-lying, possibly narrow, resonances that may exist is such models. We do so by proposing a criterion that we call partial UV completion. We characterize the simplest cases, corresponding respectively to a scalar in either singlet or tensor representation of SO(4) and to vectors in the adjoint of SO(4). We study the impact of these resonances on the signals associated to high-energy vector boson scattering, pointing out for each resonance the characteristic patterns of depletion and enhancement with respect to the leading-order chiral lagrangian. En route we derive the O( p 4) general chiral lagrangian and discuss its peculiar accidental and approximate symmetries.