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Higgs boson phenomenology and VEV shift in the RS scenario

In the framework of warped extra dimension models addressing the gauge hierarchy problem, we consider the Randall-Sundrum (RS) scenario under the usual hypothesis of a bulk custodial symmetry. It is shown in detail that there can exist large corrections to the Higgs boson Vacuum Expectation Value (VEV) induced by mixings of the gauge bosons with their Kaluza-Klein (KK) excitations. The connection with electroweak precision tests is developed. A noteworthy result is that the correct treatment of the Higgs VEV leads to an increase of the lower limit at 95% C.L. on KK masses that can reach +30% (from usually accepted values). For a Higgs mass 120 GeV < m_h < 150 GeV, the obtained limit [from updated precision data] on the first KK gauge boson mass lies in the range 3.3 - 4.0 TeV. The VEV corrections also play a central role in the corrections to the Higgs couplings. We find possibly substantial RS corrections to the various Higgs couplings able to affect its phenomenology, starting with a Higgs discovery at LHC more challenging than in the Standard Model (SM). The deviations to the Higgs production/decay rates found in RS will be testable at ILC as well as at LHC. Such RS signatures could even be used at ILC to discriminate among several models beyond the SM. Finally, the possibility of a light Higgs boson (m_h ~ 99 GeV) interpreting the excess at 2.3 Sigma observed at LEP2 is pointed out.