Search for sub-GeV Scalars in $e^+e^-$ collisions

Light scalars that couple to leptons are common figures in beyond the Standard Model endeavors. Considering a scalar that has universal and couplings to leptons only, we compute this leptophilic scalar contribution to the $e^{-}e^{+} \rightarrow \tau^{+}\tau^{-} S $ production cross section with $S \rightarrow \ell^+\ell^-$. We later compare the expected signal with recent data from the Belle collaboration collected near the resonance $\Upsilon(4S)$ with $\mathcal{L}=626 fb^{-1}$ of integrated luminosity to place limits on the couplings-mass plane for the $4$~MeV-$6.5$~GeV mass range to show that Belle stands a great laboratory for light scalars, particularly excluding part of the parameter space in which the muon g-2 anomaly is addressed.
Comment: 6 pages, 4 figures