Searching for flavor changing neutral currents in t → Hc, H → ττ decays at the LHC

The prospects of searching for the flavor changing neutral current effect in the decay of t -> H-c, H -> tau tau are investigated with the simulated p - p collision data for the ATLAS detector at the LHC, where the Higgs mass is assumed to be 125 GeV. A fit based on the constraints from the Higgs mass and the tau decay kinematics is performed for each event, which improves significantly the Higgs and top mass reconstruction and helps the signal-background separation. Boosted decision trees discriminants are developed to achieve an optimal sensitivity of searching for the flavor changing neutral current signal. An expected upper limit of the branching ratio B(t -> H-c) at 95% confidence level of 0.25% is obtained with a data set of 100 fb(-1) at root s = 13 TeV during the LHC Run-2 period.