Probing CPV mixing in the Higgs sector in VBF at 1 TeV ILC

TL;DR

This study assesses the potential of the 1 TeV ILC to measure CP violation in the Higgs sector via vector boson fusion, demonstrating high sensitivity to the CP mixing angle with simulated data.

Contribution

First analysis of an $e^{+}e^{-}$ collider's sensitivity to the CP mixing parameter in Higgs production through VBF at 1 TeV.

Findings

CP mixing angle $ heta_{CP}$ can be measured with 3.8 mrad uncertainty

Sensitivity to the CP parameter $f_{CP}$ is $1.44 imes 10^{-5}$ for a pure scalar Higgs

First sensitivity study of $f_{CP}$ measurement at an $e^{+}e^{-}$ collider in VBF

Abstract

With the current precision of measurements by the ATLAS and CMS experiments, it cannot be excluded that a SM-like Higgs boson is a CP violating mixture of CP-even and CP-odd states. We explore this possibility here, assuming Higgs boson production in ZZ-fusion, at 1 TeV ILC, with unpolarized beams. The full simulation of SM background and fast simulation of the signal is performed, simulating 8 ab$^{-1}$ of data collected with the ILD detector. We demonstrate that the CP mixing angle $\Psi_{\mathrm{CP}}$ between scalar and pseudoscalar states can be measured with the statistical uncertainty of 3.8 mrad at 68% CL, corresponding to 1.44 $\cdot 10^{-5}$ for the CP parameter $f_\mathrm{CP}$, for the pure scalar state. This is the first result on sensitivity of an $e^{+}e^{-}$ collider to measure $f_\mathrm{CP}$ in the Higgs production vertex in vector boson fusion.