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Formulation de la théorie effective à basse énergie du secteur électrofaible sans particule de Higgs

Abstract : The low-energy effective theory of electroweak symmetry-breaking without a Higgs particle is constructed using the methods of Chiral Perturbation Theory. Weinberg's power-counting formula demonstrates the consistency of the loop expansion, with the corresponding renormalization. We find that the suppression of effective operators by a mass scale, which was automatic in the case of the Standard Model, no longer holds in the Higgs-less case. Moreover, the incriminated operators appear at leading order in the chiral expansion, at variance with experiments. To account for their suppression, invariance under a larger symmetry is required, corresponding to the composite sector (which produces the three Goldstone modes) being decoupled from the elementary sector quarks, leptons and Yang-Mills fields). The couplings are introduced via spurions: this reduces the symmetry to SU(2)xU(1). In the simultaneous expansion in powers of momenta and spurions, the aforementioned operators are relegated to higher orders. In addition, the method allows for a systematic treatment of weak isospin breaking. The Weinberg power-counting formula can be recovered, and small neutrino masses accounted for. The three light-handed neutrinos (lighter than the TeV), which are introduced in connection with the custodial symmetry, are quasi-sterile and stable. A constraint on the underlying theory is obtained by studying the anomaly-matching in the composite sector and generalizing the Wess-Zumino construction. The spurion formalism is also applied to open linear moose models, for which generalized Weinberg sum rules are derived.
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Submitted on : Thursday, February 3, 2005 - 6:18:13 PM
Last modification on : Wednesday, September 16, 2020 - 4:08:14 PM
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Johannes Hirn. Formulation de la théorie effective à basse énergie du secteur électrofaible sans particule de Higgs. Physique des Hautes Energies - Expérience [hep-ex]. Université Paris Sud - Paris XI, 2004. Français. ⟨tel-00008357⟩

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