CERN Accelerating science

Leading-order production cross sections for $Z\,h$ and $h\,\nu_\ell\,\bar{\nu}_\ell$ production at an $e^+\,e^-$ collider with a com energy of 250 \GeV~ using Madgraph5 for an SM-like scalar $h$. Shown is also the contribution of $Z\,h$ to $\nu_\ell\,\bar{\nu}_\ell\,h$ using a factorized approach for the Z decay. Update of plot in \cite{Robens:2022zgk}, first presented in \cite{Robens:2022uis}.

Sensitivity predictions for an ILC with a com energy of 250 \GeV~ from \cite{Drechsel:2018mgd}. See text for details.

Upper bounds on the mixing angle for the model discussed in \cite{Wang:2020lkq}, in a comparison of different detector concepts and using the recoil method.

Upper bounds on the mixing angle for the model discussed in \cite{Wang:2020lkq}, in a comparison of different detector concepts and using the recoil method.

{\sl Left:} Points in the 2HDMs that agree with both CMS and LEP excess and which can be probed at the ILC. {\sl Right:} predicted rates in the 2HDMS and N2HDM at 250 \GeV using full target luminosity.

{\sl Left:} Points in the 2HDMs that agree with both CMS and LEP excess and which can be probed at the ILC. {\sl Right:} predicted rates in the 2HDMS and N2HDM at 250 \GeV using full target luminosity.

95 $\%$ confidence bounds on branching ratios for Higgs decay into a pair of lighter particles, for a com energy of 240~ \GeV and $\int\mathcal{L}\,=\,5\,\ab^{-1}$. Taken from \cite{Liu:2016zki}.

95 $\%$ confidence bounds on branching ratios for Higgs decay into a pair of lighter particles, for a com energy of 240~ \GeV and $\int\mathcal{L}\,=\,5\,\ab^{-1}$. Taken from \cite{Liu:2016zki}.

Expected bounds on Higgs production via Higgs strahlung and subsequent decay into two light scalars, in the singlet extension scenario discussed in \cite{Kozaczuk:2019pet,Wang:2022dkz}. {\sl Left:} Taken from \cite{Kozaczuk:2019pet}. {\sl Right:} For $\cos\theta\,=\,0$ the constraints mainly stem from $h_{125}\,\rightarrow\,\text{invisble}$ searches. Depending on $m_1$ this scenario can be tested at current or future collideer experiments.

Expected bounds on Higgs production via Higgs strahlung and subsequent decay into two light scalars, in the singlet extension scenario discussed in \cite{Kozaczuk:2019pet,Wang:2022dkz}. {\sl Left:} Taken from \cite{Kozaczuk:2019pet}. {\sl Right:} For $\cos\theta\,=\,0$ the constraints mainly stem from $h_{125}\,\rightarrow\,\text{invisble}$ searches. Depending on $m_1$ this scenario can be tested at current or future collideer experiments.

Limits on the process in eqn (\ref{eq:lims}), taken from \cite{Cepeda:2021rql}. This displays current constraints which can especially be easily reinterpreted in extended scalar sector models, in particular models where couplings are inherited via a simple mixing angle. In this figure, the lighter scalar is denoted by $s$, which corresponds to $h_i$ in the notation used in this manuscript.

Available parameter space in the TRSM, with one (high-low) or two (low-low) masses lighter than 125 \GeV. {\sl Left}: light scalar mass and mixing angle, with $\sin\al\,=\,0$ corresponding to complete decoupling. {\sl Right:} available parameter space in the $\lb m_{h_1},\,m_{h_2}\rb$ plane, with color coding denoting the rescaling parameter $\sin\al$ for the lighter scalar $h_1$. Within the green triangle, $h_{125}\,\rightarrow\,h_2 h_1\,\rightarrow\,h_1\,h_1\,h_1$ decays are kinematically allowed. Taken from \cite{Robens:2022zgk}.

Available parameter space in the TRSM, with one (high-low) or two (low-low) masses lighter than 125 \GeV. {\sl Left}: light scalar mass and mixing angle, with $\sin\al\,=\,0$ corresponding to complete decoupling. {\sl Right:} available parameter space in the $\lb m_{h_1},\,m_{h_2}\rb$ plane, with color coding denoting the rescaling parameter $\sin\al$ for the lighter scalar $h_1$. Within the green triangle, $h_{125}\,\rightarrow\,h_2 h_1\,\rightarrow\,h_1\,h_1\,h_1$ decays are kinematically allowed. Taken from \cite{Robens:2022zgk}.

Allowed regions in the 2HDM, from a scan presented in \cite{Eberhardt:2020dat}.

Mixing angle and masses of different additional scalars in the aligned 2HDM, from the scan presented in \cite{Eberhardt:2020dat}. For all additional scalars, regions exists where masses are $\lesssim\,125\,\GeV$, with absolute values of mixing angles such that $|\cos\lb\tilde{\al}\rb|\lesssim\,0.1$. Taken from \cite{Robens:2022zgk}.

Mixing angle and masses of different additional scalars in the aligned 2HDM, from the scan presented in \cite{Eberhardt:2020dat}. For all additional scalars, regions exists where masses are $\lesssim\,125\,\GeV$, with absolute values of mixing angles such that $|\cos\lb\tilde{\al}\rb|\lesssim\,0.1$. Taken from \cite{Robens:2022zgk}.

Scan results in the N2HDM, taken from \cite{Abouabid:2021yvw}. There are regions in the models parameter space where either one or two of the additional scalars have masses $\lesssim\,125\,\GeV$.