CDF Logo The Signature Lepton + Photon + b-jet with Missing Transverse Energy and a Measurement of the ttbar+Photon Cross-Section
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The unknown nature of possible new phenomena in the energy range accessible at the Tevatron is the motivation for a "signature-based" search strategy that does not focus on a single model or class of models of new physics, but presents a wide net for new phenomena. Here we present the results of a search for anomalous production of Lepton + Photon + Missing Transverse Energy (MET) + b-tagged jet events using 1.9 fb-1 of integrated luminosity from ppbar collisions at sqrt(s) = 1.96 TeV, collected using the CDF II detector. The events for the searches include production of two gauge bosons, W and photon, and two third-generation quarks, top and bottom. This search is an extension of a previous search in the lepton+photon+X signature, described in detail in Phys. Rev. D 75, 112001 (2007).

A search for the production of top pairs with an additional photon, ttbar+Photon, is a natural extension of this signature-based search, in that ttbar+Photon is characterized by the signature of a high-PT lepton, photon, b-tagged jet, and MET. When one in addition requires large total transverse energy HT (the sum of the transverse energies of the lepton, photon, jets and MET) and 3 or more jets, radiative top-pair events dominate the SM predictions.

We find 28 Lepton+Photon+MET+b events versus a standard model expectation of 27.9 +3.6/-3.5 events. We observe 16 ttbar + Photon candidate events versus an expectation of 11.1 +2.3/-2.1 events. Assuming the difference between the observed number and the predicted non-top SM total is due to top production, we measure ttbar + Photon cross-section to be 0.15+/- 0.08 pb.