Discovery potential of future electron-positron colliders for a 95 GeV scalar

The Large Electron Positron collider observed an indication for a new Higgs boson with a mass around 95 GeV-100 GeV in the process e + e − → Z * → Z S with S → b b ¯ . The interest in this excess re-emerged with the di-photon signature at ≈ 95 GeV at the Large Hadron Collider. In fact, a combined global significance of 3.4 σ is obtained once W W and τ τ signals are included in addition. In this article, we perform a feasibility study for discovering such a new scalar S at future electron-positron colliders using the recoil-mass method applied to e + e − → Z S with Z → μ + μ − and S → b b ¯ . For this, we employ a Deep Neural Network to enhance the separation between the Standard Model background and the signal, reducing the required integrated luminosity necessary for discovery by a factor of two to three. As a result, an S U ( 2 ) L singlet Higgs with a mass of ≈ 95 GeV can be observed with more than 5 σ significance at a 250 GeV centre-of-mass energy collider with 5 a b − 1 integrated luminosity if it has a mixing angle of at least 0.1 with the Standard Model Higgs, which means that a discovery can be achieved within the whole 95 % confidence-level region preferred by Large Electron Positron excess. Furthermore, including more decay channels such as S → τ τ and Z → e + e − further enhances the discovery potential of future e + e − accelerators, like CEPC, CLIC, FCC-ee and ILC.