Zt, γt and t production at hadron colliders via strong flavour-changing neutral couplings
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Aguilar-Saavedra, J.A. Zt, γt and t production at hadron colliders via strong flavour-changing neutral couplings. Nuclear Physics B, 837(1-2): 122-136 (2010). [http://hdl.handle.net/10481/30586]
PatrocinadorThis work has been partially supported by a MICINN Ramón y Cajal contract and by projects FPA2006-05294 (MICINN), FQM 101 and FQM 437 (Junta de Andalucía), CERN/FP/83588/2008 (FCT), and by the European Community's Marie-Curie Research Training Network under contract MRTN-CT-2006-035505 “Tools and Precision Calculations for Physics Discoveries at Colliders”.
We consider gq→Zt, gq→γt and gq→t production (q=u,c) mediated by strong flavour-changing neutral interactions within an effective operator framework. We provide total cross sections for Tevatron and LHC, showing explicitly that the six processes can be described in full generality in terms of only two parameters (anomalous couplings) for q=u plus two for q=c. In our work we take into account and study in detail the effects of top quark decay. For γt, the inclusion of the top quark decay in the matrix element reveals an striking result: the largest contribution to the final state, e.g.γℓνb with ℓ=e,μ,τ, does not result from gq→γt→γℓνb but from on-shell gq→t production with t→γℓνb, being the photon radiated off the top decay products. This contribution, missed in previous literature, increases the signal cross sections by factors ranging between 3 and 6.5.