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- O. Catà
- 2005

We study the issue of duality violations in the V V − AA vacuum polarization function in the chiral limit. This is done with the help of a model with an expansion in inverse powers of the number of colors, N c , allowing us to consider resonances with a finite width. Due to these duality violations, the Operator Product Expansion (OPE) and the moments of… (More)

- O Catà, S Peris
- 2001

We argue that the large-Nc expansion of QCD can be used to treat a La-grangian of resonances in a perturbative way. As an illustration of this we compute the L 10 coupling of the Chiral Lagrangian by integrating out resonance fields at one loop. This is how one can answer in a concrete and unambiguous manner questions such as at what scale resonance… (More)

- O Catà, S Peris
- 2003

Besides their appearance at short distances > ∼ 1/M W , local dimension-eight operators also contribute to kaon matrix elements at long distances of order > ∼ 1/µ ope , where µ ope is the scale controlling the Operator Product Expansion in pure QCD, without weak interactions. This comes about in the matching condition between the effective quark Lagrangian… (More)

We study the Drell-Yan production of heavy vector and axial-vector states of generic Higgsless models at hadron colliders. We analyse in particular the + − , W Z, and three SM gauge boson final states. In the + − case we show how present Tevatron data restricts the allowed parameter space of these models. The two and three gauge boson final states… (More)

- O Catà, V Mateu
- 2008

We construct the most general chirally invariant Lagrangian for mesons in the presence of external sources coupled to the tensor current ¯ ψ σ µν ψ. In order to have only even terms in the chiral expansion, we consider the new source of O(p 2). With this choice, we build the even-parity effective Lagrangian up to the p 6-order (NLO). While there are only 4… (More)

- O Catà, S Peris
- 2004

We study contributions to the ∆S = 2 weak Chiral Lagrangian producing K 0 − K 0 mixing which are not enhanced by the charm mass. For the real part, these contributions turn out to be related to the box diagram with up quarks but, unlike in perturbation theory, they do not vanish in the limit m u → 0. They increase the leading contribution to the K L −K S… (More)

We compute the fully differential rate for the Higgs-boson decay h → Z + − , with Z → + −. For these processes we assume the most general matrix elements within an effective Lagrangian framework. The electroweak chiral Lagrangian we employ assumes minimal particle content and Standard Model gauge symmetries, but it is otherwise completely general. We… (More)

We consider the Standard Model, including a light scalar boson h, as an effective theory at the weak scale v = 246 GeV of some unknown dynamics of electroweak symmetry breaking. This dynamics may be strong, with h emerging as a pseudo-Goldstone boson. The symmetry breaking scale Λ is taken to be at 4πv or above. We review the leading-order Lagrangian within… (More)

- Oscar Catà, Maarten Goltermanb
- 2008

There are some indications from recent determinations of the strong coupling constant α s and the gluon condensate that the Operator Product Expansion may not be accurate enough to describe non-perturbative effects in hadronic tau decays. This breakdown of the Operator Product Expansion is usually referred to as being due to " Duality Violations. " With the… (More)

- Oscar Catà, Maarten Golterman
- 2006

We examine whether the fact that QCD is chirally invariant at short distances necessarily leads to the prediction that hadrons form approximate parity doublets, as has been recently put forward by Glozman and collaborators. We show that this is not the case, and we exhibit some of the pitfalls of trying to link the operator product expansion to the hadron… (More)