Abstract:

The Standard Model Higgs boson must have mass between about 113 GeV and 200 GeV. The lower limit is from direct searches. The upper limit is from indirect loop effects in precision electroweak observables and might not be valid in theories beyond the Standard Model if other states conspire to cancel the effects of a heavy Higgs boson. Nevertheless, this upper limit is still an important guide to viable theories: it usually implies that either a Higgs boson will be found below 200 GeV, or that additional non-SM physics (co-conspirators) will be evident at scales accessible at the LHC and a moderate-energy e+e- linear collider.