Sensitivity of ATLAS at HL-LHC to flavour changing neutral currents in top quark decays t → cH, with H → γγ

The sensitivity of a search for flavour changing neutral currents in top quark decays t → cH, with H → γγ at HL-LHC, using the ATLAS detector is estimated. The analysis extrapolates the preliminary result obtained by ATLAS with the 7 TeV and the 8 TeV data. It is based on tt ̄ events in which one top decays to cH, the other decays to bW, and both the hadronic and the leptonic decay modes of the W are used and combined. An expected upper limit on the branching ratio of about 1.5 $\cdot10^{-4}$ at the 95% confidence level is obtained.