Enhanced Charged Higgs Signal at the LHC

TL;DR

The paper targets the discovery prospects of a charged Higgs in the G2HDM via the process $cg\to bH^+$ with $H^+\to c\bar{b}$, exploiting a potentially unsuppressed $H^+cb$ coupling proportional to $\rho_{tc} V_{tb}$. Using a full Monte Carlo framework (MG5_aMC@NLO, Pythia-8, Delphes) and realistic tagging cuts, it evaluates signal significance against dominant backgrounds $b\bar{b}j$ and $c\bar{c}j$ at $\sqrt{s}=13$–14 TeV, including MLM/CKKW-L matching and mass reconstruction via the $M_{cb_1}$ distribution. The analysis incorporates current constraints from Higgs data and flavor experiments, adopting benchmark values $\rho_{tc}=0.4$, $\rho_{ct}=0.05$, and $\rho_{tt}$ tied to $m_{H^+}$, to map discovery contours in the $(m_{H^+},\rho_{tc})$ plane. The results show promising discovery potential at the HL-LHC, especially at $\sqrt{s}=14$ TeV with $L=3000\ { m fb}^{-1}$, where $m_{H^+}$ up to about $450$ GeV could be probed for $\rho_{tc}\gtrsim 0.1$, highlighting the channel as a powerful test of the G2HDM flavor structure.

Abstract

We investigate the discovery prospects of a charged Higgs boson ($H^\pm$) at the Large Hadron Collider (LHC) via the process $cg\to bH^\pm \to bc\bar{b}$ within the framework of a general two Higgs doublet model (G2HDM). In most two Higgs doublet models, the $H^+ cb$ coupling ($g_{H^+cb}$) is usually suppressed by the CKM matrix element $V_{cb}$. In G2HDM, there are additional Yukawa couplings, the process $cg\to bH^\pm \to bc\bar{b}$ is enhanced by the coupling $g_{H^+cb} \simeq \rtc V_{tb}$ in both the production and decay of the charged Higgs boson. We study possible physics backgrounds and evaluate the discovery potential with realistic acceptance cuts and tagging efficiencies at collider energies of $\sqrt{s}=$13 and 14 TeV. We apply $b$-tagging and $c$-tagging and show that $m_{H^+}$ can be extracted by pairing the tagged $b$ and $c$-jets. Our analysis leads to promising results for the current LHC and expected high-luminosity LHC.

Figures (5)

• Figure 1: Leading-order Feynman diagrams for $cg\to bH^+$.
• Figure 2: Branching ratios of $H^+$ as a function of $m_{H^+}$ for (a) $\rho_{tc}=0.1$, and (b) $\rho_{tc}=0.4$.
• Figure 3: Invariant mass distributions $d\sigma/dM_{cb_1}$ for the signal and dominant backgrounds $b\bar{b}j$ (magenta, dashed) and $c\bar{c}j$ (black, dotted) at $\sqrt{s}=14$ TeV, shown for $\rho_{tc}=0.4$, (a) $m_{H^+}=200$ GeV (blue, solid) and (b) $m_{H^+}=400$ GeV (blue, solid).
• Figure 4: The cross section as a function of $\rho_{tc}$ for signal and background at $\sqrt{s} =$ 14 TeV after selection cuts, shown for (a) $m_{H^+}$ = 200 GeV and (b) $m_{H^+}$ = 400 GeV.
• Figure 5: The 5$\sigma$ discovery contours at the LHC in the $(m_{H^+},\rho_{tc})$ plane for (a) $\sqrt{s} =$ 13 TeV and (b) $\sqrt{s} =$ 14 TeV with $L = 300\, \text{fb}^{-1}$ (dark green solid) and $L = 3000\, \text{fb}^{-1}$ (light green dashed). In addition, 3$\sigma$ discovery contour with $L = 3000\, \text{fb}^{-1}$ (red dotted) are shown for both 13 and 14 TeV.