Probing the Higgs self-coupling at hadron colliders using rare decays

We investigate Higgs boson pair production at hadron colliders for Higgs boson masses mH<140 GeV and the rare decay of one of the two Higgs bosons. While in the standard model the number of events is quite low at the CERN Large Hadron Collider ~LHC!, a first, albeit not very precise, measurement of the Higgs boson self-coupling is possible in the gg→HH→bb̄gg channel. A luminosity-upgraded LHC could improve this measurement considerably. A 200 TeV very large hadron collider could make a measurement of the Higgs self-coupling competitive with a next-generation linear collider. In the minimal supersymmetric standard model ~MSSM! we find a significant region with observable Higgs boson pair production in the small tan b regime, where resonant production of two light Higgs bosons might be the only hint at the LHC of a MSSM Higgs sector.