The process gg → WW as a background to the Higgs signal at the LHC

The production of W pairs from the one-loop gluon fusion process is studied.Formulas are presented for the helicity amplitudes keeping the top mass finite,but all other quark masses zero. The correlations among the leptons coming fromthe W bosons are kept. The contribution of this background to the Higgs bosonsearch in the WW decay mode at the LHC is estimated by applying the cutsforeseen in experimental searches using the PYTHIA Monte Carlo program.Kinematic distributions for the final state leptons are compared to those ofthe Higgs boson signal and of the q qbar -> WW background. After applying finalcuts, the gg background is found to be large, at the level of 35% of the q qbarbackground.The characteristics of the gg background are very similar to thoseof the signal. Therefore, an experimental normalization of this backgroundcomponent appears to be very difficult and the uncertainty must largely bedetermined by theory. As a result, the significance of a Higgs signal in the gg-> H -> WW mode at the LHC is reduced.Comment: 24 pages, 4 figure