Radiative QCD backgrounds to exclusive H → b(b)over-bar production: radiation from the screening gluon

Central exclusive Higgs boson production, pp -> p circle plus H circle plus p, at the LHC can provide an important complementary contribution to the comprehensive study of the Higgs sector in a remarkably clean topology. The b (b) over bar Higgs decay mode is especially attractive, and for certain BSM scenarios may even become the discovery channel. Obvious requirements for the success of such exclusive measurements are strongly suppressed and controllable backgrounds. One potential source of background comes from additional gluon radiation which leads to a three-jet b (b) over barg final state. We perform an explicit calculation of the subprocesses gg -> q (q) over barg, gg -> ggg in the case of 'internal' gluon radiation from the spectator, t-channel screening gluon, when the two incoming active t-channel gluons form a color octet. We find that the overall contribution of this source of background is orders of magnitude lower than that caused by the main irreducible background resulting from the gg(PP) -> b (b) over bar subprocess. Therefore, this background contribution can be safely neglected.