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Backgrounds To Higgs Boson Searches from Asymmetric Internal Conversion

A class of potential backgrounds for Higgs boson searches in the W W to di-lepton channel at both the Tevatron and Large Hadron Collider is presented. Backgrounds from W photon production with external conversion of the on-shell photon in detector material to an asymmetric electron-positron pair, with loss of the trailing electron or positron has been treated adequately in Higgs searches. Here we consider analogous backgrounds from the production of a W with an off-shell photon and with the internal conversion of the off-shell photon in vacuum to an asymmetric lepton-anti-lepton pair. While the former process yields almost entirely electrons or positrons, the latter can give electron, positron, muon, and anti-muon backgrounds in roughly equal amounts. We estimate that asymmetric internal conversion backgrounds are comparable to the Higgs boson signal in the standard signal region of phase space. These processes also represent potential backgrounds for new physics searches in same-sign di-lepton channels. Some data driven methods to characterize asymmetric internal conversion backgrounds are suggested.