Top Quark FCNC Decay to 125GeV Higgs boson in the Littlest Higgs Model with T-parity

Abstract

Motivated by the current observation of a 125 GeV Higgs boson, we calculate $t\to cH$ and $t\to cg({\hat{I}}^3)H$ in the unitary gauge in the littlest Higgs model with T-parity(LHT). Due to the large contribution from the new mirror fermions, we find that the branching ratios of $t\to cH$ and $t\to cgH$ can be greatly enhanced in the LHT model and maximally reach $\mathcal{O}(10^{-5})$ in the allowed parameter space. When the mirror fermion mass $M_3>2(1.5)$ TeV and the cut-off scale $f=500$ GeV, the process of $pp \to t\bar{t} \to 3b +c +\ell+ \slashed E_{T}^{miss}$ can reach $3\ddot{I}ƒ$($5\ddot{I}ƒ$) sensitivity at 8(14) TeV LHC with luminosity $\mathcal{L}$ $=20(300)f{b}^{-1}$.

added references and discussions, updated figures, version accepted for publication in Physical Review D