ILC sensitivity for leptophilic scalar dark matter

We explore the viability of detecting a leptophilic scalar dark matter at the ILC in a simplified model approach. We present the constraints on the couplings of scalar dark matter with the standard model fermions ensuing from the relic density bounds deduced from the 2018 Planck data. We, then, present the reach of the ILC in terms of $\Lambda$, the scale of the effective theory, by performing a detailed analysis for the $Z$ associated DM pair production (i.e., $e^+ e^- \rightarrow 2$ jets + $\not \!\! E_T$, $e^+ e^- \rightarrow \mu^+ \mu^-$ + $\not \!\! E_T$ and $e^+ e^- \rightarrow e^+ e^-$ + $\not \!\! E_T$). We present the results for various run scenarios as 3-$\sigma$ contours in the $m_{\phi}-\Lambda$ plane. We also analyze the effect of beam polarization on the sensitivity of this search. We find that for the process with two hadronic jets in the final state, ILC can probe $\Lambda$ up to 1.76 TeV for $\sqrt{s}= 1$ TeV that can further enhance to 1.99 TeV, after the inclusion of polarization effects.