Effective Lagrangian approach to the EWSB sector

Abstract

In a model independent framework, the effects of new physics at the electroweak scale can be parametrized in terms of an effective Lagrangian expansion. Assuming the SU(2)LxU(1)Y gauge symmetry is linearly realized, the expansion at the lowest order span dimension–six operators built from the observed Standard model (SM) particles, in addition to a light scalar doublet. After a proper choice of the operator basis we present a global fit to all the updated available data related to the electroweak symmetry breaking sector: triple gauge boson vertex (TGV) collider measurements, electroweak precision tests and Higgs searches. In this framework modifications of the interactions of the Higgs field to the electroweak gauge bosons are related to anomalous TGV's, and given the current experimental precision, we show that the analysis of the latest Higgs boson data at the LHC and Tevatron gives rise to strong bounds on TGV's that are complementary to those from direct TGV measurements. Interestingly, we present how this correlated pattern of deviations from the SM predictions could be different for theories based on a non–linear realization of the SU(2)LxU(1)Y symmetry, characteristic of for instance composite Higgs models. Furthermore, anomalous TGV signals expected at first order in the non–linear realization may appear only at higher orders of the linear one, and viceversa. Their study could lead to hints on the nature of the observed boson.