Searches for light exotic scalar decays at the e$^+$e$^-$ Higgs factory

TL;DR

This paper investigates the potential to detect light exotic scalar particles at a future Higgs factory through various decay channels, using detailed simulations to estimate experimental sensitivities.

Contribution

It presents the expected cross section limits and sensitivities for detecting exotic light scalars at the 250 GeV Higgs factory across multiple decay modes.

Findings

Projected sensitivity in the $b\bar{b}$ decay channel.

Expected limits in $\tau^+\tau^-$ decay channel.

Sensitivity estimates for invisible decay modes.

Abstract

The physics program of the Higgs factory will focus on measurements of the 125 GeV Higgs boson, with the Higgs-strahlung process being the dominant production channel at 250 GeV. However, similar production of exotic light scalars, in a scalar-strahlug process, is still not excluded by the existing experimental data, provided their coupling to the SM gauge bosons is sufficiently suppressed. This was selected as one of the focus topics of the ECFA Higgs/Top/EW factory study. Presented are the expected cross section limits from the search in the $b\,\bar{b}$ decay channel, based on a full simulation of the International Large Detector (ILD), as well as the expected sensitivity in $\tau^+\tau^-$ and invisible decay channels, based on the fast simulation in the Delphes framework, assuming 250 GeV ILC running scenario.