A comparative study of the anomalous tHq couplings via the diphoton channel at the LHC

Abstract

We present a comparative study about the flavor changing neutral Higgs (FCNH) interactions of top quark, i.e., tqh (q=u,c), from two processes with the h→γγ decay channel: top quark pair production pp→tt¯ with one top decaying to hq, and the anomalous single top plus Higgs production process pp→th. We perform a full simulation for the signals and the relevant SM backgrounds based on two separate cut selections at the future 14 TeV High Luminosity LHC (HL-LHC). The results show that the SM background can be greatly reduced for both selection methods. The branching ratios of t→uh and t→ch can be, respectively, probed to 1.4×10−4 and 1.5×10−4 at the 95% Confidence Level (CL), which is consistent with the dedicated study performed by the ATLAS collaboration. The advantage of the pp→th process is that the origin of the signal from tuh or tch couplings could be clarified by studying the diphoton pseudo-rapidity and the charges of the charged lepton from the top decay. If we only consider the signal coming from this process, the upper limit on the branching ratio of about Br(t→uh)=2.4×10−4 at the 95% CL is obtained. Altogether, these limits are one order of magnitude better than the current 13 TeV LHC experimental results.