Probing the light charged Higgs boson, pseudoscalar Higgs boson, and $Z^\prime$ boson in the $U(1)_F$ model at the LHC

TL;DR

This work investigates the production and decay of a light charged Higgs $H^{\pm}$, a pseudoscalar $A$, and a $Z'$ boson within the flavor-dependent $U(1)_F$ extension (FDM) of the Standard Model at the LHC. It combines a detailed model-building description with collider phenomenology, applying EW, vacuum stability, perturbativity, and flavor constraints to define viable parameter space, and performs full MC simulations (MadGraph5_aMC@NLO, Pythia, Delphes) for six Benchmark Points. The analysis finds that a charged Higgs around $M_{H^{\pm}}\approx 130$ GeV could account for the ATLAS hint and shows substantial HL-LHC discovery potential for this state, particularly for $M_{H^{\pm}}\lesssim 145$ GeV; in contrast, the pseudoscalar $A$ and the $Z'$ are currently beyond reach at 14 TeV with $\mathcal{L}=300\mathrm{fb}^{-1}$ and remain challenging even at HL-LHC without tailored strategies. Overall, the paper demonstrates the feasibility of probing the FDM Higgs sector with current and near-future collider data, while highlighting the specific experimental challenges for $A$ and $Z'$ discovery.

Abstract

In this papar, we study the production and decay of a charged Higgs boson, a pseudoscalar Higgs boson, and a $Z'$ boson at the LHC within the flavor-dependent model (FDM), at the LHC. Considering the constraints from perturbative unitarity and experimental measurements (e.g., the flavor physics data, higgs signal strengths, electroweak precision observables), we investigate the relevant processes by analyzing several common LHC search channels. Motivated by the excess in $t \to b\bar{b}c$ reported by ATLAS, which suggests a charged Higgs boson with a mass near 130 GeV and consistent with B-anomaly expectations, we perform a dedicated simulation for a charged Higgs around this mass. Our results support the experimental hint and predict that this particle has a high discovery potential at the future High-Luminosity Large Hadron Collider (HL-LHC). In contrast, for the pseudoscalar and $Z'$ bosons predicted in our model, they remain beyond the reach of current experiments as well as the expected sensitivity at a 14 TeV collider with an integrated luminosity of 300 fb$^{-1}$.

Figures (7)

• Figure 1: Examples of leading-order Feynman diagrams contributing to the production of charged Higgs bosons in pp collisions: (a) single-resonant top-quark production that dominates at large $H^+$ masses, (b) double-resonant top-quark production that dominates at low $H^+$ masses.
• Figure 2: The reconstructed (a) charged Higgs boson mass, (b) top quark mass, (c) W boson mass, (d) Lepton transverse momentum, (e) $E_T^{\text{miss}}$. The signal events are generated by using BP5 in Table \ref{['t:BPs']}.
• Figure 3: The reconstructed (a) $E_T^{\text{miss}}$, (b) pseudoscalar Higgs boson mass, (c) $\tau_1$ transverse momentum, (d) $\tau_2$ transverse momentum. The signal events are generated by using BP5 in Table \ref{['t:BPs']}.
• Figure 4: The reconstructed (a) $E_T^{\text{miss}}$, (b) $Z^\prime$ boson mass, (c) $e_1$ transverse momentum, (d) $e_2$ transverse momentum. The signal events are generated by using BP5 in Table \ref{['t:BPs']}.
• Figure 5: Observed and expected 95% CL exclusion limit on cross section as a function of the charged Higgs boson mass in 36.1 $\mathrm{fb}^{-1}$ of pp collision data at $\sqrt{s} = 13 \text{TeV}$. Dots represent the cross sections of Process $pp \rightarrow t\bar{t} \rightarrow H^+ W^- b\bar{b} \rightarrow \ell^- \bar{\nu}b \bar{b}\bar{b}c$, while triangles represent the cross sections of Process $pp \to \bar{t}bH^+ \to W^- b\bar{b}tb$.