Heavy Quark Decays in the Bilepton Model

TL;DR

This work analyzes heavy-quark decays in the bilepton-331 model, focusing on $T\to Y^{++}b$ with $Y^{++}\to \mu^+\mu^+$ to produce a distinctive same-sign-dilepton final state. Using SARAH/SPheno with HiggsBounds/HiggsSignals and SSP scans, the authors identify a benchmark consistent with current constraints, predicting a 1.3 TeV bilepton and TeV-scale exotic quarks. Phenomenological studies show that at a future 100 TeV FCC-hh collider, the signal can be observed with high significance against SM backgrounds, while the LHC is unlikely to reach sensitivity. The results motivate future collider explorations of TeV-scale bileptons and vector-like quarks as viable probes of the 331 framework and physics beyond the Standard Model.

Abstract

Given the current absence of new physics signals at the LHC, it is increasingly important to investigate alternative scenarios beyond those commonly explored. In this work, we study a variant of the 331 model that predicts the existence of vector bileptons with electric charge and lepton number +/-2, as well as TeV-scale exotic quarks carrying charges +/- 5/3 and +/- 4/3. Specifically, we focus on the primary production of heavy quarks with charge +/- 5/3, which decay into a bottom quark and a bilepton, followed by the bilepton's decay into same-sign muon pairs. As a case study, we select a benchmark point that complies with current experimental exclusion limits and theoretical expectations for the bilepton mass. Our analysis shows that the resulting signal stands out clearly from Standard Model backgrounds and could be observed at a future 100 TeV hadron collider such as FCC-hh. In contrast, the LHC, even in its high-luminosity phase, lacks the sensitivity required to detect this signal.

Figures (5)

• Figure 1: Example of $T\bar{T}$ pair production at LHC or FCC-$hh$, with $T$ decaying into a bilepton and a $b$ quark
• Figure 2: Transverse momentum of the hardest (left) and next-to-hardest muon (right) for the signal (solid) and the backgrounds $b_1$ (dots) and $b_2$ (dashes).
• Figure 3: Invariant-mass distribution (left) and invariant opening angle (right) between the two hardest muons, according to the bilepton signal and the SM backgrounds . The histograms are labelled as in Fig. \ref{['ptl']}.
• Figure 4: As in Fig. \ref{['ptl']}, but displaying the pseudorapidity of the hardest lepton (left) of the angle (right) between the two hardest ones.
• Figure 5: Transverse momentum of the hardest jet (left) and invariant opening angle among hardest jet and hardest muon. Histograms are labelled like in the previous figures.