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

TL;DR

This paper investigates light leptophilic scalar particles in electron-positron collisions, analyzing their production and decay, and uses BELLE data to set new limits on their properties in the 4 MeV to 6.5 GeV mass range.

Contribution

It provides the first detailed calculation of leptophilic scalar production in $e^+e^-$ collisions and derives new experimental constraints from BELLE data, surpassing previous bounds from g-2 measurements.

Findings

Set new limits on scalar couplings in 4 MeV to 6.5 GeV range.

Demonstrated BELLE's sensitivity to light scalars.

Compared scalar signals with existing experimental data.

Abstract

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 $S \rightarrow e^{+}e^{-}(\mu^{+}\mu^{-})$. 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. We then extended this analysis to a more general one $e^{-}e^{+} \rightarrow {\ell}^{+}{\ell}^{-} S$ production cross section where $\ell=e,\mu,\tau$ with $S \rightarrow e^{+}e^{-}(\mu^{+}\mu^{-})$, showing that BELLE constitutes an excellent laboratory for light scalars, where can be derived constraints stronger than those derived stemming from the g-2 of the electron or muon.