Study of the $h{\hat{I}}^{3}Z$ coupling at the ILC

Abstract

We study the $h{\hat{I}}^{3}Z$ coupling, which is a loop induced coupling in the Standard Model (SM), to probe new physics. In a global fit based on the SM Effective Field Theory, measurement of the SM $h{\hat{I}}^{3}Z$ coupling can provide a very useful constraint, in particular for the precise determination of $hZZ$ and $hWW$ couplings. At the International Linear Collider (ILC), there are two direct ways to study the $h{\hat{I}}^{3}Z$ coupling: one is to measure the branching ratio of the $h\to {\hat{I}}^{3}Z$ decay and the other to measure the cross section for the $e^{+}{e}^{-}\to h{\hat{I}}^3$ process. We have performed a full simulation study of the $e^{+}{e}^{-}\to h{\hat{I}}^3$ process at the 250 GeV ILC, assuming 2 ab${}^{-1}$ data collected by the International Large Detector (ILD). The expected 1$\ddot{I}ƒ$ bound on the effective $h{\hat{I}}^{3}Z$ coupling ($\hat{I}{\P }_{AZ}$) combining measurements of the cross section for $e^{+}{e}^{-}\to h{\hat{I}}^3$ followed by $h\to b\bar{b}$ and the $h\to {\hat{I}}^{3}Z$ branching ratio is $-0.0015<\hat{I}{\P }_{AZ}<0.0015$. The expected significance for the signal cross section in the fully hadronic $h\to W{W}^{\ast }$ channel is 0.09 $\ddot{I}ƒ$ for beam polarizations of $P(e^{-},e^{+})=(-80\%,+30\%)$.

11 pages, 8 figures, Talk presented at the International Workshop on Future Linear Colliders (LCWS2019), Sendai, Japan, 28 October-1 November, 2019. C19-10-28. arXiv admin note: text overlap with arXiv:1902.06029