Central-edge asymmetry as a probe of Higgs-top coupling in $t\bar{t}h$ production at 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 ($A_{CE}$) to probe the CP violating Higgs-top coupling in dileptonic channel of $t\bar{t}h(\to b\bar{b})$ production at the LHC. We demonstrate that the CP-violating Higgs-top coupling can affect the central-edge asymmetry through distorting $\Delta y_{{\ell }^{+}{\ell }^{-}}$ distribution because of the contribution of new top charge asymmetric term. Since $\Delta y_{{\ell }^{+}{\ell }^{-}}$ 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 $t\bar{t}h$ production. We find that (1) the significance of dileptonic channel of $t\bar{t}h$ production can reach $5\sigma$ for CP phase $\xi =0,\pi /4,\pi /2$ when the luminosity $\mathcal{L}=795,993,1276$ fb${}^{-1}$ at 14 TeV LHC. (2) the central-edge asymmetry $A_{CE}$ show a good discrimination power of CP phase of $t\bar{t}h$ interaction, which are -40.26\%, -26.60\%, -9.47\% for $\xi =0$, $\pi /4$, $\pi /2$ respectively and are hardly affected by the event selections. Besides, by performing the binned-${\chi }^2$ analysis of $\Delta y_{{\ell }^{+}{\ell }^{-}}$ distribution, we find that the scalar and pseudo-scalar interactions can be distinguished at 95\% C.L. level at 14 TeV HL-LHC.

Comments: minor changes, version accepted by PLB