Next to minimal Higgs boson: mass bounds and search prospects

Abstract

The standard model of electroweak interactions has one scalar doublet. The minimal extension of this sector is effected by adding a neutral, singlet scalar field. Depending on whether or not the singlet field has a nonzero vacuum expectation value x, the scenario has quite distinctive predictions. In particular, x≠0 produces a mixing between the usual SU(2) doublet and the singlet, giving rise to two physical states and a Goldstone boson with a nonvanishing coupling to these. The presence of this coupling modifies the 2 jets+E/ signal of the Bjorken process at CERN LEP. We update the bounds on the Higgs boson mass using the LEP-1 data. We then explore, using parton-level Monte Carlo event generators, the production of these scalars at the CERN LHC via gluon-gluon fusion and subsequent detection. We compare the signals with the expected backgrounds.