Central-edge asymmetry as a probe of Higgs-top coupling in tt¯h production at the LHC

Abstract

The Higgs-top coupling plays a central role in the hierarchy problem and the vacuum stability of the Standard Model (SM). We propose a central-edge asymmetry (ACE) to probe the CP violating Higgs-top coupling in dileptonic channel of tt¯h(→bb¯) production at the LHC. We demonstrate that the CP-violating Higgs-top coupling can affect the central-edge asymmetry through distorting Δyℓ+ℓ− distribution because of the contribution of new top charge asymmetric term. Since Δyℓ+ℓ− distribution is frame-independent and has a good discrimination even in boosted regime, we use the jet substructure technique to enhance the observability of the dileptonic channel of tt¯h production. We find that (1) the significance of dileptonic channel of tt¯h production can reach 5σ for CP phase ξ=0,π/4,π/2 when the luminosity L=795,993,1276fb−1 at 14 TeV LHC. (2) the central-edge asymmetry ACE show a good discrimination power of CP phase of tt¯h interaction, which are −40.26%, −26.60%, −9.47% for ξ=0, π/4, π/2 respectively and are hardly affected by the event selections. Besides, by performing the binned-χ2 analysis of Δyℓ+ℓ− distribution, we find that the scalar and pseudo-scalar interactions can be distinguished at 95% C.L. level at 14 TeV HL-LHC.