Probing light scalars and vector-like quarks at the high-luminosity LHC

Abstract

A model based on a \(U(1)_{T^3_R}\) extension of the Standard Model can address the mass hierarchy between generations of fermions, explain thermal dark matter abundance, and the muon \(g - 2\), \(R_{(D)}\), and \(R_{(D^*)}\) anomalies. The model contains a light scalar boson \(\phi '\) and a heavy vector-like quark \(\chi _\textrm{u}\) that can be probed at CERN’s large hadron collider (LHC). We perform a phenomenology study on the production of \(\phi '\) and \({\chi }_u\) particles from proton–proton \((\textrm{pp})\) collisions at the LHC at \(\sqrt{s}=13.6\) TeV, primarily through \(g{-g}\) and \(t{-\chi _\textrm{u}}\) fusion. We work under a simplified model approach and directly take the \(\chi _\textrm{u}\) and \(\phi '\) masses as free parameters. We perform a phenomenological analysis considering \(\chi _\textrm{u}\) final states to b-quarks, muons, and neutrinos, and \(\phi '\) decays to \(\mu ^+\mu ^-\). A machine learning algorithm is used to maximize the signal sensitivity, considering an integrated luminosity of 3000 \(\text {fb}^{-1}\). The proposed methodology can be a key mode for discovery over a large mass range, including low masses, traditionally considered difficult due to experimental constraints.