Status of Higgs boson searches at the beginning of the LHC era

Abstract

In recent years the Tevatron Run-II collaborations have extended the search for Higgs bosons which was pioneered during the LEP accelerator operation between 1989 and 2000. This review concisely discusses the experimental constraints set by the CDF and DØ collaborations with the complete dataset taken up to September 2011. Model-independent and model-dependent limits on Higgs boson masses and couplings have been set and interpretations are discussed both in the context of the Standard Model and in extended models. In spring 2012 the Tevatron extended the excluded SM Higgs boson mass range to 147 < mH < 179 GeV at 95% CL in the high-mass region beyond the LEP limit. The summer 2012 results for the same dataset pushed the expected limit from 141 GeV down to 139 GeV, while the observed limits remained unchanged. In the low-mass region an excess of data events with respect to the background estimation is observed in the mass range 120 < mH < 135 GeV which causes the limits to be not as stringent as expected. The significance for such an excess anywhere in the full mass range is approximately 2.5σ. Focusing on the associated production of a Higgs boson with a W or Z boson and the subsequent decay of the Higgs boson to a bottom–antibottom quark pair, evidence for the presence of a new particle, consistent with the SM Higgs boson has been established, with the largest local significance of 3.3σ, corresponding to a global significance of 3.1σ. The Tevatron observation in the given mass range is consistent with the discovery of a new particle of about 125 GeV mass at the LHC. The sensitivity increase in recent years is illustrated owing to the increase in data available and improvements in analysis. The achieved experimental sensitivities are also compared to the previous predictions.