Predicting Three Generations of Fermions: Discovery Prospects of the Bilepton Model

TL;DR

This paper evaluates the discovery potential of doubly-charged bileptons at the High-Luminosity LHC, analyzing production channels and parameter sensitivities to identify promising detection scenarios.

Contribution

It introduces a comprehensive analysis of bilepton production mechanisms and their discovery prospects, highlighting the significance of heavy-quark-mediated channels at the HL-LHC.

Findings

Heavy-quark-mediated production enhances cross sections significantly.

Run-2 data can discover bileptons only if $m_D \,\lesssim\, 1$ TeV.

HL-LHC can discover bileptons up to $m_D \,\lesssim\, 2.5$ TeV and/or $m_Y \,\lesssim\, 2$ TeV.

Abstract

We study the production of pairs of doubly-charged bileptons and assess their discovery potential in light of the integrated luminosities available at the High-Luminosity LHC. The production rates are governed primarily by the bilepton mass, $(m_Y)$, and the mass of the exotic heavy quarks, $(m_D)$. We consider two complementary production channels: (i) direct bilepton pair production and (ii) bilepton production mediated through heavy-quark decays. Notably, the latter typically yields significantly enhanced cross sections and gives rise to distinctive LHC signatures, even when the bileptons are produced off-shell. The two mechanisms therefore probe complementary regions of parameter space, with direct production being predominantly sensitive to $m_Y$, while the heavy-quark-mediated channel depends mainly on $m_D$. Owing to the essentially background-free signature of four energetic leptons at the LHC, we show that Run-2 data allow a discovery only for $m_D \lesssim 1\,\mathrm{TeV}$, whereas the HL-LHC can achieve a $5\sigma$ discovery up to $m_D \lesssim 2.5\,\mathrm{TeV}$ (nearly independently of $m_Y$) and/or for $m_Y \lesssim 2\,\mathrm{TeV}$ (even if $D$ is heavy).