Probing Flavor-Violating Higgs Decays in the Type-III Two-Higgs-Doublet Model at the LHC and HL-LHC

Abstract

We present a comparative collider study of three flavor-violating Higgs signatures in the Type-III Two-Higgs-Doublet Model (\ddHmIII) at \(\sqrt{s}=14\)~TeV: \(pp \to H \to t\bar{c} \ (\bar{t}c)\), \(pp \to H^\pm \to c\bar{b} \ (\bar{c}b)\), and \(pp \to H^\pm \to t\bar{b} \ (\bar{t}b)\). Using a common cut-based analysis and realistic detector simulation, we identify a clear phenomenological hierarchy. The neutral mode and the heavy charged mode emerge as the most robust signatures, containing parameter regions that already exceed the \(5\sigma\) benchmark at an integrated luminosity of \(300~\text{fb}^{-1}\). In contrast, the light charged channel \(H^{\pm}\to c\bar{b}\) is considerably more sensitive to the event-selection strategy because of large QCD backgrounds, although one competitive benchmark survives. Our results single out the neutral and heavy charged flavor-violating channels as the most promising targets for discovery-oriented searches and for constraining the \ddHmIII\ parameter space at the LHC and HL-LHC. All quoted significances are purely statistical and do not include systematic uncertainties.