Radiative Signature of New Scalar Boson Decays in the $m_{\ell \ell {\hat{I}}^3}$ Spectrum at the LHC

Abstract

We investigate the radiative decay $S\to W^{+}{W}^{-}{\hat{I}}^3$ in the context of the multi-lepton anomalies and recent indications of a narrow scalar resonance near $m_S=152\pm 1\text{GeV}$ in the ${\hat{I}}^3{\hat{I}}^3$, $Z{\hat{I}}^3$, and $W^{+}{W}^{-}$ channels at the Large Hadron Collider. These excesses arise in final states containing leptons, missing transverse momentum, and associated $b$-jets, and motivate a search for a corresponding localized excess in the invariant-mass spectrum of the dilepton--photon system, $m_{\ell \ell {\hat{I}}^3}$, in events with associated $b$-jets. We use recent CMS measurements of the $t\bar{t}{\hat{I}}^3$ differential cross sections~\cite{CMS:2025zbe} to study the $m_{\ell \ell {\hat{I}}^3}$ spectrum and perform a search for a scalar-resonance contribution. A localized excess is observed, compatible with the scalar-resonance hypothesis, with a global significance of $2.7\ddot{I}ƒ$ at $m_S=152\text{GeV}$. This result provides additional support for the hypothesis of a narrow resonance. The ratio $\ddot{I}ƒ(S\to W^{+}{W}^{-}{\hat{I}}^3)/\ddot{I}ƒ(S\to W^{+}{W}^{-})=(2.14\pm 0.77)$\% is extracted. This value is compatible with an enhanced radiative contribution that could arise in scenarios beyond the Standard Model.

7 pages, 4 figures, 1 table