Lepton flavour violation Signals of the singly charged scalar singlet at the ILC

TL;DR

This paper explores the potential of the ILC to detect a singly charged scalar singlet through lepton flavor violation signals, setting mass exclusion limits based on different branching ratios.

Contribution

It provides the first sensitivity analysis of the ILC for detecting the singly charged scalar via LFV processes, considering current constraints and collider parameters.

Findings

Excluded scalar mass range up to 470 GeV at 95% C.L.

Sensitivity depends on the branching ratio of LFV decay.

Potential to probe scalar masses beyond current limits.

Abstract

The singly charged $SU(2)_L$ singlet scalar is one of the very interesting new particles, as it can generate neutrino masses at loop level, produce contributions to various flavour observables. We study the possibility of detecting this kind of scalar predicted by the singly-charged scalar model at ILC via the lepton flavour violation (LFV) process $e^+e^-\rightarrow S^+S^-\rightarrow \mu e + {E\mkern-10.5 mu/}$. Considering the constraints on the free parameters, we obtain the expected sensitivities of the ILC with the center of mass energy $\sqrt{s}=1~\mathrm{TeV}$ and the integrated luminosity $\mathcal{L}=$ $1.5~\mathrm{ab}^{-1}$ to the parameter space of the singly-charged scalar model. The prospective excluded mass range at $95\%$ C.L. is $M_S \gtrsim 470~\mathrm{GeV}$, $410~\mathrm{GeV}$ for the branching ratio $\mathcal{B}_{\mu e}$ = $100\%$ , $50\%$, respectively, while the scalar with $M_S \gtrsim 300~\mathrm{GeV}$ is excluded at $95\%$ C.L. for $\mathcal{B}_{\mu e}$ = $30\%$.