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Seminario
"Gauge Symmetry Breaking through Boundary conditions, Can we live without the Higgs ?"

Relatore: Dott. Luigi Pilo- Dip. di Fisica, Un. di Padova and INFN, Padova

Aula Einstein
16 Dicembre 2003 ore 15.30

Abstract
:We consider the breaking of gauge symmetry through boundary conditions (BC's) extra dimensional gauge theories on an interval. To investigate the nature of gauge symmetry breaking via BC's we calculate the elastic scattering amplitudes for longitudinal gauge bosons. We find that using a consistent set of BC's the terms in these amplitudes that explicitly grow with energy always cancel without having to introduce any additional scalar degree of freedom, but rather by the exchange of Kaluza--Klein (KK) gauge bosons suggesting that perhaps the SM Higgs could be completely eliminated. We show that from the low-energy effective theory perspective this seems to be indeed possible. We present a 5D gauge theory in warped space based on a bulk $SU(2)_L otimes SU(2)_R otimes U(1)_{(B-L)}$ gauge group where the symmetry breaking pattern and the mass spectrum resembles that in the standard model (SM). To leading order in the warp factor the rho parameter and the coupling of the Z (or equivalently the S-parameter) are as in the SM, while corrections are expected at the level of a percent. This model predicts the lightest W, Z and photon resonances to be at around 1.2 TeV, and no fundamental (or composite) Higgs particles.