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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
- 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)

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 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)

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 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)

We consider the electroweak chiral Lagrangian, including a light scalar boson, in the limit of small ξ = v 2 /f 2. Here v is the electroweak scale and f is the corresponding scale of the new strong dynamics. We show how the conventional SILH Lagrangian, defined as the effective theory of a strongly-interacting light Higgs (SILH) to first order in ξ , can be… (More)

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)

- Oscar Catà
- 2005

Recent sum rule analyses on the <VV-AA> two-point correlator have led to significant discrepancies in the values found for the OPE condensates, most dramatically in the dimension eight condensate and to a lesser extent in the dimension six one [1]. Precise knowledge of these condensates is of relevance in kaon decays [2] and therefore it seems mandatory to… (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)