One-loop gg→b(b)over-bar effects in the main irreducible background to exclusive H→b(b)over-bar production at the LHC

We calculate the amplitude of gg -> b (b) over bar production for the colour singlet, J(z) = 0, di-gluon state at O(alpha(2)(S)) order. We consider the cancellation and a realistic cut-off, of the infrared divergent terms. We show that the one-loop radiative QCD contributions effectively reduce the Born level result for the central exclusive b (b) over bar cross section at the LHC. This process is essentially the only irreducible QCD background to the exclusive H -> b (b) over bar signal.