Single top quark production as a probe of anomalous tqγ and tqZ couplings at the FCC-ee
Hamzeh Khanpour (School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran, Department of Physics, University of Science and Technology of Mazandaran, P.O. Box 48518-78195, Behshahr, Iran)
; Sara Khatibi (School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran); Morteza Khatiri Yanehsari (School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran); Mojtaba Mohammadi Najafabadi (School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran)
In this paper, a detailed study to probe the top quark Flavour-Changing Neutral Currents (FCNC) tqγ and tqZ at the future eâe+ collider FCC-ee in two different center-of-mass energies of 240 and 350 GeV is presented. A set of useful variables are proposed and used in a multivariate technique to separate signal eâe+âZ/γâtq¯ (t¯q) from Standard Model background processes. The study includes a fast detector simulation based on the delphes package to consider the detector effects. The upper limits on the FCNC branching ratios at 95% confidence level (CL) in terms of the integrated luminosity are presented. It is shown that with 300 fbâ1 of integrated luminosity of data, FCC-ee would be able to exclude the effective coupling strengths above O(10â4â10â5) which is corresponding to branching fraction of O(0.01â0.001) %. We show that moving to a high-luminosity regime leads to a significant improvement on the upper bounds on the top quark FCNC couplings to a photon or a Z boson.
