Single-top production in the $tW^\pm$ channel and Higgs signals via $H\to W^+W^-$ at the Large Hadron Collider

In a recent study by Dittmar and Dreiner it was shown that with appropriate selection cuts the signature of events containing two charged leptons and missing energy represents the best chance of detecting the Standard Model Higgs scalar in the mass range between 155 and 180 GeV, the primary decay of the Higgs being into pairs of charged gauge bosons. The largest background to this channel is due to irreducible $W^+W^-X$ production. In the present paper we calculate the contribution of events of the type $bg\to tW^\pm\to b W^+W^-\to b \ell^{+}\ell^{'-}\nu_\ell\bar\nu_{\ell'}$, which have not been considered yet within the new selection strategy. We show that the yield of this background is rather large, at the level of that produced by $W^+W^-$, $t\bar t$ or $tb W^\pm$ events and thus needs to be incorporated in future experimental analyses. However, we find that its inclusion will not spoil the possibilities of Higgs detection in the above mentioned channel at the Large Hadron Collider.