On radiative QCD backgrounds to exclusive H -> b bbar production at the LHC and a photon collider

Central exclusive Higgs boson production, pp -> p + H + p, at the LHC and s-channel resonant Higgs production in the photon-collider option of the ILC can provide a very important contribution to the comprehensive study of the Higgs sector. Especially attractive is the b bbar Higgs decay mode, which for certain MSSM scenarios may become the discovery channel in exclusive Higgs production at the LHC and the Photon Collider (PC). Strongly suppressed and controllable backgrounds is an obvious requirement for the success of these exclusive measurements. One of the main sources of background comes from additional gluon radiation which leads to a three-jet b bbar g final state. We perform an explicit calculation of the subprocesses gg -> q qbar g and gamma gamma -> q qbar g, where the incoming particles are required to be in a J_z=0 state and the two gluons form a colour singlet, and investigate the salient properties of these potentially important background processes.