J. M. Matías

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We justify the feasibility of substituting a photon leg by a neutrino current in the Euler–Heisenberg Lagrangian to obtain an effective Lagrangian for the process γν → γγν and its crossed reactions. We establish the link between these processes and the four-photon scattering in both the Standard Model and the effective theory. As an application, we compute(More)
In a wide class of new-physics models, which can be motivated through generic arguments and within supersymmetry, we obtain large contributions to B 0 d –B 0 d mixing, but not to ∆B = 1 processes. If we assume such a scenario, the solutions φ d ∼ 47 • ∨ 133 • for the B 0 d –B 0 d mixing phase implied by A mix CP (B d → J/ψK S) cannot be converted directly(More)
We provide a set of sum rules relating CP-averaged branching ratios and CP-asymmetries of the B → πK modes. They prove to be useful as a mechanism to 'test' experimental data given our expectations of the size of isospin breaking. A set of observables emerges providing a simpler interpretation of data in terms of isospin breaking. Moreover, the derivation(More)
We consider an extension of the standard electroweak theory with gauge group SU (2) L × SU (2) R × U (1) ˜ Y , where the gauge bosons of the extra SU (2) R factor do not couple to ordinary fermions. We show that precision electroweak data and flavour physics provide quite stringent indirect constraints on its parameter space, but still allow for relatively(More)
We perform an exhaustive analysis of the Equivalence Theorem both in the minimal Standard Model and in an Effective Electroweak Chiral Lagrangian up to O(p 4). We have considered the leading corrections to the usual prescription consisting in just replacing longitudinally polarized W or Z by the corresponding Goldstone bosons. The corrections appear through(More)
We analyze the matching conditions to determine the values that the O(p 4) coefficients of an Effective Chiral Lagrangian take in the Standard Model in the limit of a large Higgs mass, pointing out a number of subtleties that appear to have gone unnoticed previously. We apply the resulting Effective Chiral Lagrangian, including the leading two loop effects,(More)